Praziquantel is still very effective for the treatment of schistosomiasis, but there are rising concerns on the potential risk of developing resistances because of the extensive use of this drug. Triclabendazole, a systemic anthelmintic, is very effective against other trematodes such as Paragonimus spp. and Fasciola spp. It has been reported to be effective in vitro and in experimental animals against Schistosoma mansoni. However, its antischistosomal efficacy in humans has not yet been evaluated. The objective of the study was to evaluate the efficacy of triclabendazole at the dosage currently used for the treatment of human fascioliasis (10mg/kg body weight) in subjects co-infected with S. mansoni and Fasciola spp. The study was carried out in Behera, a highly endemic area for both parasites, by personnel of the Egyptian Ministry of Health and Population. Ten subjects (m = 4, f = 6; age, 8-58years), who were infected at the same time by Fasciola spp. and S. mansoni, were enrolled. Six weeks after therapy, seven subjects were still excreting ova of S. mansoni, whereas none was excreting Fasciola spp. ova. At the given dosage, triclabendazole appeared not to be sufficiently effective in the treatment of S. mansoni.