The value of the 6-day subrenal capsule assay (SRCA) in predicting the effectiveness of chemotherapy was tested using three human choriocarcinomas. The SRCA method proved to be a valuable chemopredictive test for choriocarcinoma. The results of experimental chemotherapy in nude mice and the results of the SRCA in two types of choriocarcinoma correlated well. Two of three choriocarcinomas showed sensitivity to MAC combination chemotherapy [methotrexate, actinomycin D, cyclophosphamide), and all three showed greater sensitivity to VP-16. The administration of VP-16 for treatment of all three types of choriocarcinoma significantly reduced tumor size in a dose-dependent fashion. From these observations, we speculate that the SRCA may be applied to assess the effectiveness of chemotherapy against human choriocarcinoma.