The antitrypanosomal activity of 101 crude ethanol extracts derived from 88 medicinal plants from Côte d'Ivoire was determined in vitro using Trypanosoma brucei rhodesiense. Of those extracts 8 showed good activity (IC50 values < or =8 microg/ml), 37 revealed a weak activity (IC50 values between 25 and 8.1 microg/ml) and 56 did not show any activity at all (IC50 values >25 microg/ml). The extracts of Enantia polycarpa (Annonaceae) and Trichilia emetica (Meliaceae) were the most promising ones. Their IC50 values were 0.5 and 0.04 microg/ml, respectively, and the selectivity index 616 and 209, respectively. This is the first report of in vitro antitrypanosomal activity of these two plants. Their high activities render them candidates for the isolation of compounds which could develop into new lead structures for drug development programs against African trypanosomiasis. Seven of the tested extracts exhibited an antiplasmodial activity against K1 strain of Plasmodium falciparum with IC50 values below 4 microg/ml. The highest activity was found for Enantia polycarpa stem bark with an IC50 value of 0.126 microg/ml.