diff --git a/inc/functions.php b/inc/functions.php
index e6ca2b0..f1ba00f 100644
--- a/inc/functions.php
+++ b/inc/functions.php
@@ -8,6 +8,7 @@
 use RebelCode\Atlas\Expression\ColumnTerm;
 use RebelCode\Atlas\Expression\ExprInterface;
 use RebelCode\Atlas\Expression\Term;
+use RebelCode\Atlas\Expression\VarExpr as ArgExpr;
 
 /**
  * Creates a new column term.
@@ -218,3 +219,8 @@ function andAll(iterable $exprs): ?ExprInterface
         return $result;
     }
 }
+
+function arg(string $name): ArgExpr
+{
+    return new ArgExpr($name);
+}
diff --git a/src/DatabaseAdapter.php b/src/DatabaseAdapter.php
index 4f50827..a01f362 100644
--- a/src/DatabaseAdapter.php
+++ b/src/DatabaseAdapter.php
@@ -7,6 +7,25 @@
 /** An adapter for a database connection that allows queries created by Atlas to be executed. */
 interface DatabaseAdapter
 {
+    /**
+     * Gets the placeholder to use for a value before preparing the query.
+     *
+     * @param string $name The name of the value.
+     * @param mixed $value The value.
+     * @return string The placeholder string, such as '?'.
+     */
+    public function getPlaceholder(string $name, $value): string;
+
+    /**
+     * Replaces ??{var}?? placeholders in the SQL with '?' and collects the
+     * values in the order they appear in the string.
+     *
+     * @param string $sql The SQL string
+     * @param list<mixed> $values The values
+     * @return array{0:string,1:list<mixed>} The SQL and var values.
+     */
+    public function prepare(string $sql, array $values): array;
+
     /**
      * Executes a query that returns results.
      *
@@ -14,7 +33,7 @@ interface DatabaseAdapter
      * @return array<string,mixed>[] A list of rows, where each row is a map of column names to values.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    public function queryResults(string $sql): array;
+    public function queryResults(string $sql, array $args = []): array;
 
     /**
      * Executes a query and returns the number of affected rows.
@@ -23,7 +42,7 @@ public function queryResults(string $sql): array;
      * @return int The number of affected rows.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    public function queryNumRows(string $sql): int;
+    public function queryNumRows(string $sql, array $args = []): int;
 
     /**
      * Executes a query and returns whether the query was successful.
@@ -32,7 +51,7 @@ public function queryNumRows(string $sql): int;
      * @return bool True if the query was successful, false otherwise.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    public function query(string $sql): bool;
+    public function query(string $sql, array $args = []): bool;
 
     /**
      * Gets the value generated for an AUTO_INCREMENT column by the last query.
diff --git a/src/Expression/VarExpr.php b/src/Expression/VarExpr.php
new file mode 100644
index 0000000..e3f55d3
--- /dev/null
+++ b/src/Expression/VarExpr.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace RebelCode\Atlas\Expression;
+
+class VarExpr extends BaseExpr
+{
+    protected string $name;
+
+    public function __construct(string $name)
+    {
+        $this->name = $name;
+    }
+
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    protected function toBaseString(): string
+    {
+        return '??{' . $this->name . '}??';
+    }
+}
diff --git a/src/Query.php b/src/Query.php
index 540c794..0a5e6ca 100644
--- a/src/Query.php
+++ b/src/Query.php
@@ -46,8 +46,42 @@ abstract public function toSql(): string;
     /**
      * Executes the query.
      *
+     * @param array<string,mixed> $args A map of values to interpolate. The keys
+     *        correspond to {@link VarExpr} names.
      * @return mixed The query result.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    abstract public function exec();
+    abstract public function exec(array $args = []);
+
+    /**
+     * Replaces ??{var}?? placeholders in the SQL with '?' and collects the
+     * values in the order they appear in the string.
+     *
+     * @param string $sql The SQL string
+     * @param array $args An array of args, mapping each arg name to its value.
+     * @return array{0:string,1:list<mixed>} The SQL and var values.
+     */
+    protected function templateVars(string $sql, array $args)
+    {
+        if (count($args) === 0) {
+            return [$sql, []];
+        }
+
+        $vars = [];
+        $result = preg_replace_callback(
+            '/(\?\?\{([\w\d_]+)\}\?\?)/im',
+            function (array $match) use ($args, &$vars) {
+                $name = trim($match[2] ?? '');
+                if (empty($name) && !array_key_exists($name, $args)) {
+                    return $match[1];
+                }
+                $value = $args[$name];
+                $vars[] = $value;
+                return $this->adapter->getPlaceholder($name, $value);
+            },
+            $sql
+        );
+
+        return [$result, $vars];
+    }
 }
diff --git a/src/Query/CompoundQuery.php b/src/Query/CompoundQuery.php
index 7f45bab..428defa 100644
--- a/src/Query/CompoundQuery.php
+++ b/src/Query/CompoundQuery.php
@@ -48,11 +48,11 @@ public function toSql(): string
     }
 
     /** @inheritDoc */
-    public function exec()
+    public function exec(array $args = [])
     {
         $results = [];
         foreach ($this->queries as $query) {
-            $results[] = $query->exec();
+            $results[] = $query->exec($args);
         }
 
         return $results;
diff --git a/src/Query/CreateIndexQuery.php b/src/Query/CreateIndexQuery.php
index 0c15d74..184a2a8 100644
--- a/src/Query/CreateIndexQuery.php
+++ b/src/Query/CreateIndexQuery.php
@@ -75,8 +75,10 @@ public function toSql(): string
      *
      * @return bool True if the index was created successfully, false otherwise.
      */
-    public function exec(): bool
+    public function exec(array $args = []): bool
     {
-        return $this->getAdapter()->query($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->query($sql, $values);
     }
 }
diff --git a/src/Query/CreateTableQuery.php b/src/Query/CreateTableQuery.php
index 27b8cf8..28f1715 100644
--- a/src/Query/CreateTableQuery.php
+++ b/src/Query/CreateTableQuery.php
@@ -94,8 +94,10 @@ protected function compileSchema(Schema $schema): string
      *
      * @return bool True if the query was executed successfully, false otherwise.
      */
-    public function exec(): bool
+    public function exec(array $args = []): bool
     {
-        return $this->getAdapter()->query($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->query($sql, $values);
     }
 }
diff --git a/src/Query/DeleteQuery.php b/src/Query/DeleteQuery.php
index 40abc43..30cfdba 100644
--- a/src/Query/DeleteQuery.php
+++ b/src/Query/DeleteQuery.php
@@ -80,8 +80,10 @@ public function toSql(): string
      * @return int The number of rows affected by the query.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    public function exec(): int
+    public function exec(array $args = []): int
     {
-        return $this->getAdapter()->queryNumRows($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->queryNumRows($sql, $values);
     }
 }
diff --git a/src/Query/DropTableQuery.php b/src/Query/DropTableQuery.php
index 9def937..371192a 100644
--- a/src/Query/DropTableQuery.php
+++ b/src/Query/DropTableQuery.php
@@ -65,8 +65,10 @@ public function toSql(): string
      *
      * @return bool True if the table was dropped, false if not.
      */
-    public function exec(): bool
+    public function exec(array $args = []): bool
     {
-        return $this->getAdapter()->query($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->query($sql, $values);
     }
 }
diff --git a/src/Query/InsertQuery.php b/src/Query/InsertQuery.php
index 5be10a7..ba3024b 100644
--- a/src/Query/InsertQuery.php
+++ b/src/Query/InsertQuery.php
@@ -153,10 +153,12 @@ protected function compileInsertValues(): string
      *
      * @return int|null The last inserted ID, or null if no rows were inserted.
      */
-    public function exec(): ?int
+    public function exec(array $args = []): ?int
     {
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
         $adapter = $this->getAdapter();
-        $numRows = $adapter->queryNumRows($this->toSql());
+        $numRows = $adapter->queryNumRows($sql, $values);
 
         if ($numRows > 0) {
             return $adapter->getInsertId();
diff --git a/src/Query/SelectQuery.php b/src/Query/SelectQuery.php
index 4089e4b..c8947ec 100644
--- a/src/Query/SelectQuery.php
+++ b/src/Query/SelectQuery.php
@@ -220,8 +220,10 @@ public function compileSource(): string
      *
      * @return array<string,mixed>[] A list of rows, where each row is a map of column names to values.
      */
-    public function exec(): array
+    public function exec(array $args = []): array
     {
-        return $this->getAdapter()->queryResults($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->queryResults($sql, $values);
     }
 }
diff --git a/src/Query/UpdateQuery.php b/src/Query/UpdateQuery.php
index 097a286..ac33c46 100644
--- a/src/Query/UpdateQuery.php
+++ b/src/Query/UpdateQuery.php
@@ -83,8 +83,10 @@ public function toSql(): string
      * @return int The number of rows affected by the query.
      * @throws DatabaseException If an error occurred while executing the query.
      */
-    public function exec(): int
+    public function exec(array $args = []): int
     {
-        return $this->getAdapter()->queryNumRows($this->toSql());
+        [$sql, $values] = $this->templateVars($this->toSql(), $args);
+
+        return $this->getAdapter()->queryNumRows($sql, $values);
     }
 }
diff --git a/tests/Query/SelectQueryTest.php b/tests/Query/SelectQueryTest.php
index 721c8b6..3072437 100644
--- a/tests/Query/SelectQueryTest.php
+++ b/tests/Query/SelectQueryTest.php
@@ -2,11 +2,14 @@
 
 namespace RebelCode\Atlas\Test\Query;
 
+use PHPUnit\Framework\MockObject\MockClass;
+use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use RebelCode\Atlas\DatabaseAdapter;
 use RebelCode\Atlas\DataSource;
 use RebelCode\Atlas\Expression\ColumnTerm;
 use RebelCode\Atlas\Expression\ExprInterface;
+use RebelCode\Atlas\Expression\VarExpr;
 use RebelCode\Atlas\Group;
 use RebelCode\Atlas\Join;
 use RebelCode\Atlas\Order;
@@ -14,6 +17,8 @@
 use RebelCode\Atlas\Query\SelectQuery;
 use RebelCode\Atlas\Test\Helpers\ReflectionHelper;
 
+use function RebelCode\Atlas\andAll;
+use function RebelCode\Atlas\arg;
 use function RebelCode\Atlas\col;
 use function RebelCode\Atlas\table;
 
@@ -467,4 +472,31 @@ public function testNotExists()
 
         $this->assertEquals("NOT EXISTS(SELECT * FROM `test` WHERE (`role` = 'admin'))", $exists->toSql());
     }
+
+    public function testWithVars()
+    {
+        $args = ['foo' => 'VALUE1', 'bar' => 'VALUE2'];
+
+        $adapter = $this->createMock(DatabaseAdapter::class);
+        $adapter->expects($this->exactly(2))
+            ->method('getPlaceholder')
+            ->withConsecutive(['bar', 'VALUE2'], ['foo', 'VALUE1'])
+            ->willReturnOnConsecutiveCalls('<bar>', '<foo>');
+
+        $adapter->expects($this->once())
+            ->method('queryResults')
+            ->with(
+                'SELECT * FROM `test` WHERE ((`name` = <bar>) AND (`age` = <foo>))',
+                ['VALUE2', 'VALUE1']
+            );
+
+        $query = (new SelectQuery($adapter))
+            ->from(table('test'))
+            ->where(andAll([
+                col('name')->eq(arg('bar')),
+                col('age')->eq(arg('foo')),
+            ]));
+
+        $query->exec($args);
+    }
 }