Effects of extracts of Euphorbia pulcherima and Atriplex nummularia on infection rate and cercarial production of Bulinus truncatus infected with Schistosoma haematobium, as well as on the free living stages of the parasite (miracidia and cercariae) besides biochemical parameters of the snail were studied. The results showed that the LC25 of the extracts of E. pulcherima and A. nummularia caused a considerable reduction in the infectivity of S. haematobium miracidia to the snail. It caused a reduction in the number of cercariae per snail during the period of cercarial shedding. The mortality rates of the miracidia and cercariae were elevated gradually by increasing the exposure period to the extracts of these plants. The results obtained also revealed that the glucose concentrations increased in haemolymph, while soft tissue glycogen and protein contents were decreased. The activities of hexokinase, pyruvate kinase and lactate dehydrogenase were also significantly reduced in response to treatment, while adenosine triphosphatase (ATPase) activity of the tissue of the snails was significantly increased.