Glutaminase is a hematotoxic anti-tumor agent, and copper–ATP complex (Cu–ATP) is both anti-neoplastic and hematostimulatory. Combination chemotherapy with these two agents has been performed in mice bearing Ehrlich ascites carcinoma, to elucldate whether this could result in augmented tumor inhibition with reduced hematotoxicity. Glutaminase–Cu–ATP combination (glutaminase 250 IU/kg per day Intraperitoneally for 10 days and Cu–ATP 2.5 mg/kg per day intraperitoneally for 10 days) was observed to be more effective in inhibiting tumor growth and in increasing the life span of the tumor hosts, compared with the individual efficacies of these two agents. Moreover, addition of Cu–ATP successfully prevented the hematotoxic effects of glutaminase in normal and in tumor-bearing animals. Thus glutaminase in combination with Cu–ATP holds promise for an effective cancer chemotherapeutic regimen.