diff --git a/lib/Makefile.local b/lib/Makefile.local
index 36c39243..76b57cb2 100644
--- a/lib/Makefile.local
+++ b/lib/Makefile.local
@@ -49,6 +49,7 @@ libnotmuch_cxx_srcs =		\
 	$(dir)/index.cc		\
 	$(dir)/message.cc	\
 	$(dir)/query.cc		\
+	$(dir)/config.cc	\
 	$(dir)/thread.cc
 
 libnotmuch_modules := $(libnotmuch_c_srcs:.c=.o) $(libnotmuch_cxx_srcs:.cc=.o)
diff --git a/lib/config.cc b/lib/config.cc
new file mode 100644
index 00000000..9ca74bf5
--- /dev/null
+++ b/lib/config.cc
@@ -0,0 +1,87 @@
+/* config.cc - API for database metadata
+ *
+ * Copyright © 2016 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#include "notmuch.h"
+#include "notmuch-private.h"
+#include "database-private.h"
+
+static const std::string CONFIG_PREFIX = "C";
+
+notmuch_status_t
+notmuch_database_set_config (notmuch_database_t *notmuch,
+			     const char *key,
+			     const char *value)
+{
+    notmuch_status_t status;
+    Xapian::WritableDatabase *db;
+
+    status = _notmuch_database_ensure_writable (notmuch);
+    if (status)
+	return status;
+
+    try {
+	db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
+	db->set_metadata (CONFIG_PREFIX + key, value);
+    } catch (const Xapian::Error &error) {
+	status = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+	notmuch->exception_reported = TRUE;
+	_notmuch_database_log (notmuch, "Error: A Xapian exception occurred setting metadata: %s\n",
+			       error.get_msg().c_str());
+    }
+    return NOTMUCH_STATUS_SUCCESS;
+}
+
+static notmuch_status_t
+_metadata_value (notmuch_database_t *notmuch,
+		 const char *key,
+		 std::string &value)
+{
+    notmuch_status_t status = NOTMUCH_STATUS_SUCCESS;
+
+    try {
+	value = notmuch->xapian_db->get_metadata (CONFIG_PREFIX + key);
+    } catch (const Xapian::Error &error) {
+	status = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+	notmuch->exception_reported = TRUE;
+	_notmuch_database_log (notmuch, "Error: A Xapian exception occurred getting metadata: %s\n",
+			       error.get_msg().c_str());
+    }
+    return status;
+}
+
+notmuch_status_t
+notmuch_database_get_config (notmuch_database_t *notmuch,
+			     const char *key,
+			     char **value)
+{
+    std::string strval;
+    notmuch_status_t status;
+
+    if (! value)
+	return NOTMUCH_STATUS_NULL_POINTER;
+
+    status = _metadata_value (notmuch, key, strval);
+    if (status)
+	return status;
+
+    *value = strdup (strval.c_str ());
+
+    return NOTMUCH_STATUS_SUCCESS;
+}
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 3a092efc..c827e02d 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -1838,6 +1838,26 @@ notmuch_filenames_move_to_next (notmuch_filenames_t *filenames);
 void
 notmuch_filenames_destroy (notmuch_filenames_t *filenames);
 
+
+/**
+ * set config 'key' to 'value'
+ *
+ */
+notmuch_status_t
+notmuch_database_set_config (notmuch_database_t *db, const char *key, const char *value);
+
+/**
+ * retrieve config item 'key', assign to  'value'
+ *
+ * keys which have not been previously set with n_d_set_config will
+ * return an empty string.
+ *
+ * return value is allocated by malloc and should be freed by the
+ * caller.
+ */
+notmuch_status_t
+notmuch_database_get_config (notmuch_database_t *db, const char *key, char **value);
+
 /**
  * interrogate the library for compile time features
  */
diff --git a/test/T590-libconfig.sh b/test/T590-libconfig.sh
new file mode 100755
index 00000000..85e44979
--- /dev/null
+++ b/test/T590-libconfig.sh
@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+test_description="library config API"
+
+. ./test-lib.sh || exit 1
+
+add_email_corpus
+
+cat <<EOF > c_head
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <notmuch.h>
+
+void run(int line, notmuch_status_t ret)
+{
+   if (ret) {
+	fprintf (stderr, "line %d: %s\n", line, ret);
+	exit (1);
+   }
+}
+
+#define RUN(v)  run(__LINE__, v);
+
+int main (int argc, char** argv)
+{
+   notmuch_database_t *db;
+   char *val;
+   notmuch_status_t stat;
+
+   RUN(notmuch_database_open (argv[1], NOTMUCH_DATABASE_MODE_READ_WRITE, &db));
+
+EOF
+
+cat <<EOF > c_tail
+   RUN(notmuch_database_destroy(db));
+}
+EOF
+
+test_begin_subtest "notmuch_database_{set,get}_config"
+cat c_head - c_tail <<'EOF' | test_C ${MAIL_DIR}
+{
+   RUN(notmuch_database_set_config (db, "testkey1", "testvalue1"));
+   RUN(notmuch_database_set_config (db, "testkey2", "testvalue2"));
+   RUN(notmuch_database_get_config (db, "testkey1", &val));
+   printf("testkey1 = %s\n", val);
+   RUN(notmuch_database_get_config (db, "testkey2", &val));
+   printf("testkey2 = %s\n", val);
+}
+EOF
+cat <<'EOF' >EXPECTED
+== stdout ==
+testkey1 = testvalue1
+testkey2 = testvalue2
+== stderr ==
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_done