To examine the cardiotoxic effect of adriamycin on cultured rat myocardial cells, cytotoxicity was measured by MTT assay after cultured myocardial cells were grown with various concentrations of adriamycin(ADA) for 48 hours. The protective effect of Benincasae Semen(BS) on ADR-induced cardiotoxicity was also examined in these cultures. ADR decreased cell viability of cultured rat myocardial cells remarkably in a dose- and time-dependent manners. In protective effect of BS, it was very effective in blocking ADR-induced cytotoxicity. From these results, it is suggested that ADR shows cardioxicity, and the herba extract, as is very effective in preventing ADR-induced cytotoxicity on cultured rat myocardial cells.