Coca-Erythroxylum coca Lamarck var. coca-remains one of the most common plants of the folk medicine of Bolivia used as a general stimulant. Aymara and Quechua natives prefer to chew the sweeter coca leaves from the Yungas (tropical mountain forests of the eastern slopes of the Andes) rather than those from the Chapare lowlands. The contents in cocaine and minor constituents of leaf samples cultivated in these regions does not rationalize this choice.