The effects of shock waves in combination with various anti-cancer agents i.e. Bleomycin (BLM), Cisplatin (CDDP) and 5-fluorouracil (5-FU) on tumor cells suspended in media containing these agents were examined. GCIY cells derived from human gastric cancer and LS 174T and SW480 cells derived from human colon cancers were used for in vitro experiments; GCIY and SW480 cells were also transplanted into nude mice for in vivo study. It was only with BLM that enhancement was evident in all three cell lines, with a degree of chemotherapeutic enhancement proportional to the amount of shock wave energy applied. Ladder formation of DNA in GCIY cells was observed only when treated with both BLM and shock waves in combination. When SW480 and GCIY cells transplanted into the backs of nude mice were treated with a combination of intravenously (i.v.) injected BLM and regional exposure to shock waves, a significant enhancement of chemotherapeutic effects was observed in terms of the tumor growth curve.