Coca continues to supply the major share of farm income in the three countries and to employ most inhabitants. Further, despite extensive transfers of economic, law enforcement, and military assistance from the United States between 1988 and 1992, coca cultivation increased by 20 percent and potential coca leaf output by 13 percent. Two lessons seem especially relevant from the crop substitution experience: (1) despite a secular decline in coca prices since the mid-1980's, coca cultivation continues to be an attractive proposition for farmers; and (2) farmers have adopted successful strategies to continue cultivating coca in the face of government pressure to switch to legal economic activities. The outlook for crop substitution programs appears particularly bleak in Peru and Colombia. In Peru, the sheer size of the coca trade represents a major challenge. Coca occupies almost 130,000 hectares, accounts for 15 to 20 percent of Peru's legal agricultural product, and employs 9 percent of the agricultural work force in the country. In Colombia, most coca cultivation occurs in regions where the Colombian government does not exercise effective control. The best arguments for retaining crop substitution programs are political rather than economic. Such programs function as useful negotiating tools with coca producers, and assistance to coca-growing regions may improve the image of both the United States and the host government. The best hope for reducing Andean coca cultivation, however, rests with enforcement measures that depress coca prices and wear down farmers and with development programs that promote solid growth throughout the national economy as a whole. Footnotes, tables, figures, photographs, and maps