The effect of a combination of shock waves with cisplatin was examined in vivo with subcutaneously implanted amelanotic melanomas (A-Mel 3) in Syrian golden hamsters and cisplatin-sensitive or cisplatin-resistant fibrosarcoma (SSK2/0 and SSK2/R2) in C3H mice. In all 3 tumor models, 4 treatment modalities were compared: control, cisplatin treatment, shock waves and the combination of shock waves and cisplatin. Shock waves significantly delayed tumor growth in all 3 tumor models when compared to the respective control group. Cisplatin alone delayed the growth of A-Mel 3 and SSK2/0, whereas SSK2/R2 remained uninfluenced by the drug. In all 3 tumor models the combined treatment with shock waves and cisplatin additively and significantly delayed tumor growth. In A-Mel-3-bearing animals the combined treatment significantly increased survival time. The growth of SSK2/0 and SSK2/R2 tumors was delayed to a similar extent by the combined treatment modality as compared to shock-wave treatment alone. This indicates that the cisplatin resistance of SSK2/R2 tumors has been overcome by the simultaneous shock wave treatment. An increased intracellular cisplatin accumulation in the tumors due to shock wave exposure is suggested as the mechanism of interaction between shock waves and cisplatin.