The assessment determined the extent to which the program has over time reduced the amount of heroin and marijuana entering the United States from Mexico and whether Mexico is using the U.S. aircraft in an efficient manner. The study also determined whether the formal bilateral agreements provide an adequate basis for the ongoing cooperation needed to eradicate the marijuana and poppy fields as quickly and efficiently as possible. Data indicate that between 1977 and 1980, the eradication program, benefited by poor weather, achieved significant decreases in the availability of Mexican heroin and marijuana in the United States. The efficiency and effectiveness of the program could be improved through a better information base for planning, enhanced personnel and resource management, and more effective administration of the aviation operations. The formal agreements could be improved by addressing the methodology for surveys of the cultivation base, the setting of eradication targets, the measurement of eradication accomplishments, and periodic evaluation and audit.