Crinum stuhlmannii Baker (Amaryllidaceae) is one of the ca. 40 known species of the genus Crinum found in Africa. Bulbs of various Crinum species have been used to treat various ailments like coughs and colds, renal and hepatic conditions, sores, sexually transmitted diseases, and backache. In this paper we report the isolation of 8 alkaloids; lycorine, 9-O-demethylpluviine, kirkine, ambelline, crinamine, crinine, hamayne, and amabiline. Lycorine and crinamine showed biological activity against Entamoeba hystolytica (strain HK9, and trophozoites stage) with IC50 values of 0.23 μg/ml and 0.53 μg/ml, respectively. Ambelline showed no activity. Omidazol, used as the standard, had an IC50 of 0.28 μg/ml. The three compounds showed no activity against Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum.