This article uses experimental data to test for a complementary relationship between formal regulations imposed on a community to conserve a local natural resource and nonbinding verbal agreements to do the same. Our experiments were conducted in the field in three regions of Colombia. Our results suggest that the hypothesis of a complementary relationship between communication and external regulation is supported for some combinations of regions and regulations but cannot be supported in general. We conclude that the determination of whether formal regulations and informal communication are complementary must be made on a community-by-community basis. (JEL C93, H41, Q20, Q28)