An account of Banisteria Caapi Spruce as a drug plant of the Amazonian lndians is given. The chromosomes of three cultivated plants from different sources were examinied: the 2n-number is 20; the chromosomes have median or submedian constrictions. The plants studied did not differ vegetatively; they were not brought to flower. No other chromosome-number reports are known for the Malpighiaceae.