diff --git a/amplpy/ampl.pyx b/amplpy/ampl.pyx
index d390d21..405da34 100644
--- a/amplpy/ampl.pyx
+++ b/amplpy/ampl.pyx
@@ -465,6 +465,7 @@ cdef class AMPL:
 
         PY_AMPL_CALL(campl.AMPL_GetOption(self._c_ampl, name.encode('utf-8'), &exists, &value_c))
         value = value_c.decode('utf-8')
+        campl.AMPL_StringFree(&value_c)
         if exists:
             try:
                 return int(value)
diff --git a/amplpy/dataframe.pxi b/amplpy/dataframe.pxi
index 18060d7..c2a0cc1 100644
--- a/amplpy/dataframe.pxi
+++ b/amplpy/dataframe.pxi
@@ -243,8 +243,9 @@ cdef class DataFrame(object):
         if len(value) == 1 and isinstance(value[0], (tuple, list)):
             value = value[0]
         assert len(value) == self._get_num_cols()
-        cdef campl.AMPL_TUPLE* py_tuple = to_c_tuple(tuple(value))
-        campl.AMPL_DataFrameAddRow(self._c_df, py_tuple)
+        cdef campl.AMPL_TUPLE* tuple_c = to_c_tuple(tuple(value))
+        campl.AMPL_DataFrameAddRow(self._c_df, tuple_c)
+        campl.AMPL_TupleFree(&tuple_c)
 
     def _add_column(self, header, values=None):
         """
@@ -341,6 +342,7 @@ cdef class DataFrame(object):
         cdef size_t index
         cdef campl.AMPL_TUPLE* tuple = to_c_tuple(key)
         campl.AMPL_DataFrameGetRowIndex(self._c_df, tuple, &index)
+        campl.AMPL_TupleFree(&tuple)
         return Row.create(self._c_df, index)
 
     def _get_row_by_index(self, index):
@@ -365,7 +367,11 @@ cdef class DataFrame(object):
         cdef size_t size
         cdef char** headers
         campl.AMPL_DataFrameGetHeaders(self._c_df, &size, &headers)
-        return tuple(headers[i].decode('utf-8') for i in range(size))
+        headers_py = tuple(str(headers[i].decode('utf-8')) for i in range(size))
+        for i in range(size):
+            campl.AMPL_StringFree(&headers[i])
+        free(headers)
+        return headers_py
 
     def _set_values(self, values):
         """
diff --git a/amplpy/entity.pxi b/amplpy/entity.pxi
index 1dcd6f5..4f8eadc 100644
--- a/amplpy/entity.pxi
+++ b/amplpy/entity.pxi
@@ -49,8 +49,10 @@ cdef class Entity(object):
         return entity
 
     #def __dealloc__(self):
-    #    if self._index is not NULL:
-    #        campl.AMPL_TupleFree(&self._index)
+    #    if self._name is not NULL:
+    #        campl.AMPL_StringFree(&self._name)
+        #if self._index is not NULL:
+        #    campl.AMPL_TupleFree(&self._index)
 
     def to_string(self):
         cdef char* output_c
@@ -111,9 +113,12 @@ cdef class Entity(object):
         campl.AMPL_EntityGetTuples(self._c_ampl, self._name, &indices_c, &size)
         for i in range(size):
             if campl.AMPL_TupleCompare(index_c, indices_c[i]) == 0:
+                for j in range(size):
+                    campl.AMPL_TupleFree(&indices_c[j])
                 free(indices_c)
                 return create_entity(self.wrap_function, self._c_ampl, self._name, index_c)
         free(indices_c)
+        campl.AMPL_TupleFree(&index_c)
         return None
 
     def instances(self):
diff --git a/amplpy/environment.pxi b/amplpy/environment.pxi
index 830f6d0..09f5384 100644
--- a/amplpy/environment.pxi
+++ b/amplpy/environment.pxi
@@ -73,7 +73,6 @@ cdef class Environment(object):
         cdef const char* to_string_c
         campl.AMPL_EnvironmentToString(self._c_env, &to_string_c)
         to_string = str(to_string_c.decode('utf-8'))
-        #campl.AMPL_StringFree(&to_string_c)
         return to_string
 
     def set_bin_dir(self, binary_directory):
@@ -92,7 +91,6 @@ cdef class Environment(object):
         cdef const char* bin_dir_c
         campl.AMPL_EnvironmentGetBinaryDirectory(self._c_env, &bin_dir_c)
         bin_dir = str(bin_dir_c.decode('utf-8'))
-        #campl.AMPL_StringFree(&bin_dir_c)
         return bin_dir
 
     def set_bin_name(self, binary_name):
@@ -111,7 +109,6 @@ cdef class Environment(object):
         cdef const char* bin_name_c
         campl.AMPL_EnvironmentGetBinaryName(self._c_env, &bin_name_c)
         bin_name = str(bin_name_c.decode('utf-8'))
-        #campl.AMPL_StringFree(&(<char*>bin_name_c))
         return bin_name
     
     # Aliases
diff --git a/amplpy/util.pxi b/amplpy/util.pxi
index 89e6e7d..3ef3f85 100644
--- a/amplpy/util.pxi
+++ b/amplpy/util.pxi
@@ -72,7 +72,7 @@ cdef void setValues(campl.AMPL* ampl, char* name, campl.AMPL_TUPLE* index, value
     campl.AMPL_SetInstanceSetValuesTuples(ampl, name, index, values_c, size)
 
     for i in range(size):
-        free(values_c[i])
+        campl.AMPL_TupleFree(&values_c[i])
     free(values_c)
 
 cdef to_py_variant(campl.AMPL_VARIANT* variant):
@@ -103,6 +103,7 @@ cdef to_py_tuple(campl.AMPL_TUPLE* tuple_c):
     return tuple(pylist)
 
 cdef campl.AMPL_TUPLE* to_c_tuple(py_tuple):
+    cdef size_t i
     cdef campl.AMPL_TUPLE* tuple_c
 
     if not isinstance(py_tuple, (tuple, list)):
@@ -116,6 +117,9 @@ cdef campl.AMPL_TUPLE* to_c_tuple(py_tuple):
 
     campl.AMPL_TupleCreate(&tuple_c, size, variants)
 
+    for i in range(size):
+        campl.AMPL_VariantFree(&variants[i])
+
     free(variants)
     return tuple_c