The study found that U.S. Government assistance has improved international counter-narcotic cooperation with the eight major drug transit countries with criminal organizations that transport hundreds of tons of illegal drugs from South America to the United States through a six-million square mile “transit zone” that includes Central America, the Caribbean, the Gulf of Mexico, and the eastern Pacific Ocean. First, assistance programs have helped partner nations collect, process, and share information and intelligence that have led to arrests and drug seizures. Second, assistance programs have enabled these nations to participate in counter-narcotic operations by providing equipment, logistical support, and training to police units. Third, United States assistance has helped strengthen the capacity of prosecutors to work more effectively on drug-related cases. Despite these gains in international cooperation, however, several factors, including resource limitations and lack of political will, have impeded U.S. efforts to assist governments become full and self-sustaining partners in the counter-narcotic efforts. Programs for building maritime drug-interdiction capacity have been particularly affected by lack of fuel and other resources required to operate and maintain boats provided by the United States. GAO recommends that the U.S. State Department report more comprehensively and consistently on the results of U.S. initiatives and develop plans for sustaining U.S.-provided assets. GAO also recommends that the Department of Homeland Security (DHS) determine the feasibility of expanding its Container Security Initiative in targeting and scanning containers for illicit drugs. GAO analyzed relevant data, met with United States and foreign officials, and visited selected countries. 5 tables, 3 figures, and appended details on the study’s scope and methodology, counter-narcotics maritime law enforcement agreements, comments from DHS, comments from the U.S. Department of Justice, comments from the U.S. Drug Enforcement Administration, and comments from the Office of National Drug Control Policy