Exposure of mice fibroblasts cell strain 3T3 to high energy shock waves and megavoltage radiotherapy resulted in a reduction in cell viability as determined by trypan-blue exclusion and H3-Thymidine incorporation assays. Electromagnetic shock waves have a higher cytotoxic effect on cell viability than megavoltage radiotherapy, at low and medium levels of energy. Megavoltage radiotherapy has a higher cytotoxic effect on cell viability at high levels of energy, as nucleoside incorporation reveals. The combination of electromagnetic shock waves and megavoltage radiotherapy delivered on cell cultures at medium levels of energy, did not enhance their cytotoxicity when it was compared with their high levels of energy individually.