Release of Echinostoma caproni cercariae and Schistosoma mansoni from experimentally infected Biomphalaria glabrata snails maintained under different laboratory conditions was studied. Infected snails were isolated individually for 1 h in Stender dishes containing 5 ml of artificial spring water and the number of cercariae released during this time was recorded. Of numerous conditions tested, the addition of lettuce, the use of water conditioned by B. glabrata snails and a temperature of 35°C significantly increased the release of E. caproni cercariae. A significant increase in cercarial release of S. mansoni was seen only in cultures fed lettuce. A temperature of 12°C caused a significant decrease in cercarial release of both E. caproni and S. mansoni. Increased snail activity associated with feeding behaviour was probably responsible for the enhanced cercarial sheds observed in this study.