It was investigated whether preliminary administration of water with reduced Deuterium content may modify the inhibitory effect of the water given to BDF1 and CDA mice on the day of tumor transplantation. Two models were used: Lewis lung carcinoma (LLC) and uterine cervical carcinoma (UCC). Experimental mice (20 per group) used the water with reduced Deuterium content. Water with a Deuterium content close to that of drinking water was given to controls (30 per group). Both kinds of water were given to mice 4 weeks before the experiment. Inhibitory effect was acknowledged by the time at which the first nodules appeared at site of transplantation and assessed with respect to volume of tumor and animal life-span. Metastasis inhibition coefficient was determined for Lewis carcinoma metastasizing to the lung. It was found that water with reduced Deuterium content effectively inhibited the growth of the transplantable tumors under study, significantly reduced metastasis weight in mice with LLC and increased life-span in animals with transplantable UCC.