Abstract: Some coumarin compounds containing a lactone ring have definite anthelmintic effect. Thus, fifty seven compounds of substituted coumarin-3-carboxylic esters and amides have been synthesized.After screening with mice, six of them were found to possess pronounced anthelmintic activity against Schistosomiasis japonica, among which ethyl 6-bromo-coumarin-3-carboxylate was shown to be the most effective and has passed on to clinical trials with promising results.