AIM: To investigate the antitumor effect of recombinant L-asparaginase on the growth of several tumors such as P388, L1210, hepatocellular carcinoma (Heps), K562, P815, and sarcoma 180 (S180). METHODS: Tumor cells (K562, L1210, and P815) were cultured in vitro and the morphology of those cells was observed with inverse microscope and transmission electron microscope. MTT assay was performed to measure the cell proliferation and inhibition rate. DNA content was assayed by flow cytometry. According to protocols of transplant tumor research, mice were transplanted with tumor cells LI210, P388, Heps, and S180. The survival rate and weight of tumor were observed after the treatment of test drugs. RESULTS: The antimmor effects of L-asparaginase were observed in vitro with tumor cells K562, L1210, and P815 (P<0.01). In vivo experiments showed that ip adminis-tration of L-asparaginase significantly increased the survival rate and life span of mice with P388 or LI210 tumor cells (P<0.01). Tumor growth induced with Heps was also significantly suppressed. Furthermore, significant suppression of tumor growth was observed in mice induced with Heps and S180 by iv administration of L-asparaginase. CONCLUSION: Recombinant L-asparaginase markedly inhibited tumors tested in this study and the results strongly suggest that recombinant L-asparagiuase has great potential for clinical treatment of these tumors.