Haitian Vodou priests (houngans) and priestesses (mambos) use plant remedies to treat many illnesses, including intestinal parasite infections. The present study screened 12 plants used in Vodou treatments for intestinal parasites to detect in vitro activity against infective-stage larvae of the hookworm Ancylostoma caninum. Water-soluble extracts of 4 of the 12 plants inhibited serum-stimulated feeding by larval A. caninum in a dose-dependent manner. All 4 plant extracts inhibited feeding induced by the muscarinic agonist arecoline, suggesting that these plant extracts may inhibit the insulin-like signaling pathway involved in the recovery and resumption of development of arrested A. caninum larvae. These results indicate that at least some of the plants used in traditional Haitian medicine as vermifuges show activity against nematode physiological processes.