The primary method for the control of schistosomiasis has been via an attack on the intermediate molluscan host either through environmental control or the use of molluscicides. The present study offers a new approach to the problem, through the suppression or destruction of the parasite within the snail. Chloramphenicol, an inhibitor of protein synthesis, provides complete suppression of the formation of cercariae from miracidia at concentrations as low as 20 ppm, as long as the snails are exposed to the drug. The drug has been shown to prevent the formation of mother sporocysts and to inhibit the development of cercariae from daughter sporocysts. The effect of chloramphenicol on protein synthesis-related processes appears to be selective as evidenced by ratios of complete parasite suppression to snail LD50, snail growth and snail egg-laying. Although chloramphenicol may not itself offer a practical field method for the control of schistosomiasis, it may lead to the finding of a more effective means of controlling the disease by the study and exploitation of this new approach to the problem.