diff --git a/onnxscript/analysis.py b/onnxscript/analysis.py
index 0998663423..30ca18e055 100644
--- a/onnxscript/analysis.py
+++ b/onnxscript/analysis.py
@@ -37,10 +37,8 @@ def used_vars(expr: Optional[ast.expr]) -> Set[str]:
     return result
 
 
-def local_defs(lhs: ast.expr) -> Set[str]:
-    """Utility function to return set of assigned/defined
-    variables in the lhs of an assignment statement.
-    """
+def lhs_vars(lhs: ast.expr) -> Set[str]:
+    """Return set of assigned variables in the lhs of an assignment statement."""
 
     def get_id(e):
         assert isinstance(e, ast.Name), "Only simple assignments supported."
@@ -51,27 +49,33 @@ def get_id(e):
     return {get_id(lhs)}
 
 
-def defs(stmt: ast.stmt) -> Set[str]:
-    """Return the set of all variables that may be defined (assigned to) in an
-    execution of input stmt.
+def assigned_vars(
+    stmt: ast.stmt | list[ast.stmt], formatter: sourceinfo.Formatter
+) -> Set[str]:
+    """Return the set of all variables that may be assigned to in an execution of input stmt
+    or sequence of statements.
     """
 
-    def block_defs(block: Sequence[ast.stmt]) -> Set[str]:
+    def assigned_in_block(block: Sequence[ast.stmt]) -> Set[str]:
         result: set[Any] = set()
         for s in block:
-            result = result | defs(s)
+            result = result | assigned_vars(s, formatter)
         return result
 
     if isinstance(stmt, ast.Assign):
-        return local_defs(stmt.targets[0])
+        return lhs_vars(stmt.targets[0])
     if isinstance(stmt, ast.AnnAssign):
-        return local_defs(stmt.target)
+        return lhs_vars(stmt.target)
     if isinstance(stmt, ast.Return):
         return set()
     if isinstance(stmt, ast.If):
-        return block_defs(stmt.body) | block_defs(stmt.orelse)
+        return assigned_in_block(stmt.body) | assigned_in_block(stmt.orelse)
+    if isinstance(stmt, ast.For):
+        return assigned_in_block(stmt.body) | {get_loop_var(stmt, formatter)}
+    if isinstance(stmt, ast.While):
+        return assigned_in_block(stmt.body)
     if isinstance(stmt, list):
-        return block_defs(stmt)
+        return assigned_in_block(stmt)
     if isinstance(stmt, ast.Break):
         return set()
     if ast_utils.is_print_call(stmt):
@@ -98,9 +102,9 @@ def visitBlock(block: Sequence[ast.stmt], live_out: Set[str]) -> Set[str]:
             return live_out
 
         if isinstance(stmt, ast.Assign):
-            return live_out.difference(local_defs(stmt.targets[0])) | used_vars(stmt.value)
+            return live_out.difference(lhs_vars(stmt.targets[0])) | used_vars(stmt.value)
         if isinstance(stmt, ast.AnnAssign):
-            return live_out.difference(local_defs(stmt.target)) | used_vars(stmt.value)
+            return live_out.difference(lhs_vars(stmt.target)) | used_vars(stmt.value)
         if isinstance(stmt, ast.Return):
             return used_vars(stmt.value)
         if isinstance(stmt, ast.If):
@@ -170,9 +174,9 @@ def visitBlock(block: Sequence[ast.stmt], live_out: Set[str]) -> Set[str]:
 
     def visit(stmt: ast.stmt, live_out: Set[str]) -> Set[str]:
         if isinstance(stmt, ast.Assign):
-            return live_out.difference(local_defs(stmt.targets[0])) | used_vars(stmt.value)
+            return live_out.difference(lhs_vars(stmt.targets[0])) | used_vars(stmt.value)
         if isinstance(stmt, ast.AnnAssign):
-            return live_out.difference(local_defs(stmt.target)) | used_vars(stmt.value)
+            return live_out.difference(lhs_vars(stmt.target)) | used_vars(stmt.value)
         if isinstance(stmt, ast.Return):
             return used_vars(stmt.value)
         if isinstance(stmt, ast.If):
diff --git a/onnxscript/analysis_test.py b/onnxscript/analysis_test.py
index 362d44dab9..3ec14ad628 100644
--- a/onnxscript/analysis_test.py
+++ b/onnxscript/analysis_test.py
@@ -163,5 +163,57 @@ def nested():  # pylint: disable=unused-variable
         self.assertUses(f, {"x"})
 
 
+class TestAssignedVarAnalysis(unittest.TestCase):
+    def assert_assigned_vars(self, f, expected: set[str]):
+        source, parse_tree = ast_utils.get_src_and_ast(f)
+        result = analysis.assigned_vars(parse_tree.body, formatter(source))
+        self.assertEqual(result, expected)
+
+    def test_basic_defs(self):
+        def f(x):
+            x = x + 1
+            y = x + 2
+            return y
+
+        self.assert_assigned_vars(f, {"x", "y"})
+
+    def test_if_defs(self):
+        def f(x):
+            if x > 1:
+                y = x + 1
+                z = 2 * y
+            else:
+                t = x + 2
+                z = 3 * t
+            return z
+
+        self.assert_assigned_vars(f, {"z", "y", "t"})
+
+    def test_loop_defs(self):
+        def f(x):
+            sum = 0
+            while x > 0:
+                x = x - 1
+                square = x * x
+                sum = sum + square
+            return sum
+
+        self.assert_assigned_vars(f, {"sum", "x", "square"})
+
+    def test_if_loop_defs(self):
+        def f(x):
+            if x > 0:
+                sum = 0
+                while x > 0:
+                    x = x - 1
+                    square = x * x
+                    sum = sum + square
+            else:
+                sum = 0
+            return sum
+
+        self.assert_assigned_vars(f, {"sum", "x", "square"})
+
+
 if __name__ == "__main__":
     unittest.main(verbosity=2)
diff --git a/onnxscript/converter.py b/onnxscript/converter.py
index 9b121a5b38..4c2f9c859d 100644
--- a/onnxscript/converter.py
+++ b/onnxscript/converter.py
@@ -1102,9 +1102,11 @@ def ret(exp, i, suffix):
 
     def translate_if_stmt(self, stmt: ast.If) -> None:
         if hasattr(stmt, "live_out"):
-            live_defs = list(stmt.live_out.intersection(analysis.defs(stmt)))
+            live_defs = list(
+                stmt.live_out.intersection(analysis.assigned_vars(stmt, self.message))
+            )
         else:
-            live_defs = list(analysis.defs(stmt))
+            live_defs = list(analysis.assigned_vars(stmt, self.message))
         test = self.translate_expr(stmt.test, "cond").name
         lineno = self.source_of(stmt).lineno
         thenGraph, sub_fct_then = self.translate_block(
@@ -1183,7 +1185,7 @@ def translate_loop_stmt(self, loop_stmt: Union[ast.For, ast.While]) -> None:
             self.fail(loop_stmt, f"Unexpected loop type {type(loop_stmt)!r}.")
         # analyze loop body
         exposed_uses = analysis.exposed_uses(loop_stmt.body, self.message)
-        vars_def_in_loop = analysis.defs(loop_stmt.body)
+        vars_def_in_loop = analysis.assigned_vars(loop_stmt.body, self.message)
         loop_state_vars = vars_def_in_loop.intersection(exposed_uses | loop_stmt.live_out)
         scan_outputs = set()  # TODO
         outputs = list(loop_state_vars | scan_outputs)
diff --git a/onnxscript/converter_test.py b/onnxscript/converter_test.py
index 74b68bf2a9..ce955b7d29 100644
--- a/onnxscript/converter_test.py
+++ b/onnxscript/converter_test.py
@@ -655,6 +655,18 @@ def float_list_as_tensor():
         expected = np.array([13, 17], dtype=np.float32).reshape((2,))
         self.check_run(float_list_as_tensor, [], expected)
 
+    def test_loop_inside_if(self):
+        @script(default_opset=op)
+        def sum(n: INT64) -> INT64:
+            sum = op.Constant(value=0)
+            if n > 0:
+                for i in range(n):
+                    sum = sum + i
+            return sum
+
+        self.check_run(sum, [np.array(5, dtype=np.int64)], np.array(10, dtype=np.int64))
+        self.check_run(sum, [np.array(-5, dtype=np.int64)], np.array(0, dtype=np.int64))
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)