diff --git a/.gitignore b/.gitignore
index 55d325a..cb4331a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ bench_internal
 tests
 exhaustive_tests
 gen_context
+valgrind_ctime_test
 *.exe
 *.so
 *.a
diff --git a/Makefile.am b/Makefile.am
index 79dcf6e..e73b1ba 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -93,6 +93,12 @@ if USE_TESTS
 noinst_PROGRAMS += tests
 tests_SOURCES = src/tests.c
 tests_CPPFLAGS = -DSECP256K1_BUILD -I$(top_srcdir)/src -I$(top_srcdir)/include $(SECP_INCLUDES) $(SECP_TEST_INCLUDES)
+if VALGRIND_ENABLED
+tests_CPPFLAGS += -DVALGRIND
+noinst_PROGRAMS += valgrind_ctime_test
+valgrind_ctime_test_SOURCES = src/valgrind_ctime_test.c
+valgrind_ctime_test_LDADD = libsecp256k1.la $(SECP_LIBS) $(SECP_TEST_LIBS) $(COMMON_LIB)
+endif
 if !ENABLE_COVERAGE
 tests_CPPFLAGS += -DVERIFY
 endif
diff --git a/configure.ac b/configure.ac
index a2023ab..e4929d6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -556,6 +556,7 @@ echo "  scalar                  = $set_scalar"
 echo "  ecmult window size      = $set_ecmult_window"
 echo "  ecmult gen prec. bits   = $set_ecmult_gen_precision"
 echo
+echo "  valgrind                = $enable_valgrind"
 echo "  CC                      = $CC"
 echo "  CFLAGS                  = $CFLAGS"
 echo "  CPPFLAGS                = $CPPFLAGS"
diff --git a/src/valgrind_ctime_test.c b/src/valgrind_ctime_test.c
new file mode 100644
index 0000000..04c06d4
--- /dev/null
+++ b/src/valgrind_ctime_test.c
@@ -0,0 +1,100 @@
+/**********************************************************************
+ * Copyright (c) 2020 Gregory Maxwell                                 *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#include <valgrind/memcheck.h>
+#include "include/secp256k1.h"
+#include "util.h"
+
+#if ENABLE_MODULE_ECDH
+# include "include/secp256k1_ecdh.h"
+#endif
+
+int main(void) {
+    secp256k1_context* ctx;
+    secp256k1_ecdsa_signature signature;
+    secp256k1_pubkey pubkey;
+    size_t siglen = 74;
+    size_t outputlen = 33;
+    int i;
+    int ret;
+    unsigned char msg[32];
+    unsigned char key[32];
+    unsigned char sig[74];
+    unsigned char spubkey[33];
+
+    if (!RUNNING_ON_VALGRIND) {
+        fprintf(stderr, "This test can only usefully be run inside valgrind.\n");
+        fprintf(stderr, "Usage: libtool --mode=execute valgrind ./valgrind_ctime_test\n");
+        exit(1);
+    }
+
+    /** In theory, testing with a single secret input should be sufficient:
+     *  If control flow depended on secrets the tool would generate an error.
+     */
+    for (i = 0; i < 32; i++) {
+        key[i] = i + 65;
+    }
+    for (i = 0; i < 32; i++) {
+        msg[i] = i + 1;
+    }
+
+    ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_DECLASSIFY);
+
+    /* Test keygen. */
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_ec_pubkey_create(ctx, &pubkey, key);
+    VALGRIND_MAKE_MEM_DEFINED(&pubkey, sizeof(secp256k1_pubkey));
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret);
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, spubkey, &outputlen, &pubkey, SECP256K1_EC_COMPRESSED) == 1);
+
+    /* Test signing. */
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_ecdsa_sign(ctx, &signature, msg, key, NULL, NULL);
+    VALGRIND_MAKE_MEM_DEFINED(&signature, sizeof(secp256k1_ecdsa_signature));
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret);
+    CHECK(secp256k1_ecdsa_signature_serialize_der(ctx, sig, &siglen, &signature));
+
+#if ENABLE_MODULE_ECDH
+    /* Test ECDH. */
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_ecdh(ctx, msg, &pubkey, key, NULL, NULL);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret == 1);
+#endif
+
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_ec_seckey_verify(ctx, key);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret == 1);
+
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_ec_privkey_negate(ctx, key);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret == 1);
+
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    VALGRIND_MAKE_MEM_UNDEFINED(msg, 32);
+    ret = secp256k1_ec_privkey_tweak_add(ctx, key, msg);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret == 1);
+
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    VALGRIND_MAKE_MEM_UNDEFINED(msg, 32);
+    ret = secp256k1_ec_privkey_tweak_mul(ctx, key, msg);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret == 1);
+
+    /* Test context randomisation. Do this last because it leaves the context tainted. */
+    VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
+    ret = secp256k1_context_randomize(ctx, key);
+    VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
+    CHECK(ret);
+
+    secp256k1_context_destroy(ctx);
+    return 0;
+}