Recent fieldwork in the eastern lowlands of Bolivia and Peru has revealed a traditional use of coca (Erythroxylum coca Lam.) as a medicine and stimulant that is distinct from the well-documented customs of the Northwest Amazon and the Andean highlands. In Bolivia some nine indigenous tribes centered mainly in the Rio Beni drainage masticate entire sun-dried coca leaves yet use as an alkaline additive the crude ash of the spathe or leafbase of the motacv? palm (Scheelea princeps (Mart.) Karst.). To the quid they add a piece of the bark of the bignoniaceous liana chamairo (Mussatia sp.) which markedly sweetens the chew. In the montav±a of Peru the liana is also used and a new species is reported from the upper Apurimac river. The ethnobotany of chamairo throughout its range is examined and the need for pharmacological screening is emphasised.