The diterpenoid furanolactone (columbin) from Aristolochia albida inhibited growth of culture forms of Trypanosoma brucei. In vitro analysis of the compound at 5-250 microg/ml showed complete lysis of the parasites within 10-20 minutes post incubation. At 50 microg/ml, columbin killed about 50% of the parasites which initially appeared swollen under phase contrast microscopy. Also the total amount of cholesterol diminished dose-dependently in the presence of 10-100 microg/ml of columbin after a 3-day incubation period. In vivo analysis of the compound in T. brucei-infected mice revealed that 25 mg/kg administered for 3 consecutive days, completely cleared the parasites from the peripheral circulation. However, columbin could not clear parasites in the cerebrospinal fluid.