Recent habitat degradation within the desert areas of the southwestern United States and adjoining areas of Mexico has seriously depleted endemic fish populations. During the past 35 years, 4 species and 6 subspecies in 6 genera apparently have become extinct within California, Nevada, and Arizona, and at least 50 additional species and subspecies within 8 Great Basin states and northern Mexico are considered threatened. Of these, 19 are currently listed as endangered by the Secretary of the Interior. The urgency and complexity of the problem caused several governmental agencies to combine in 1970 with other concerned parties and form the Desert Fishes Council. This was done to improve communications and assist in the development of an interagency preservation program, the primary purpose of which was to reduce the rate of habitat destruction. A Pupfish Task Force established by the Department of the Interior in 1970 coordinated efforts of that agency and initiated an effective program based upon protection of native habitats. The Desert Fishes Council continues as an active participant. The methodology developed may prove useful in solving similar problems as they occur elsewhere.