Embelia schimperi Vatke, belonging to the family Myrsinaceae, is used among the traditional Masai people of Tanzania and Kenya since it is believed to eliminate adult Taenia saginata, the beef tapeworm. In the present study, the anthelmintic effect of an extract of the dried fruits of Embelia schimperi was studied in experimental parasite/rodent models. In two experiments, rats with 10 adult tapeworms of Hymenolepis diminuta were treated with a diammonium salt of embelin (DE), isolated from the fruits. Significant lower numbers and total worm biomass of Hymenolepis diminuta were observed in rats treated with 100 mg DE/kg. Furthermore, clear indications of the occurrence of destrobilation was observed in faeces after treatment and in 16% of the worms found at autopsy. The killing effect shown in vivo was corroborated by in vitro studies, which showed that all adult Hymenolepis diminuta were killed when incubated in a culture medium containing as little as 0.08 mg DE/ml. No significant in vivo effect of DE was observed against Hymenolepis microstoma, the trematode Echinostoma caproni and the nematode Heligmosomoides polygyrus in mice, although the worms could be killed in vitro. These results indicate that the crushed seeds of Embelia schimperi taken orally by the Masai people indeed have an anthelmintic effect against human intestinal tapeworms.