The authors transplanted Ehrlich ascites tumor (EAT) cells to 90 inbred mice of CBA strain in order to investigate the role that sex of animal and dose of tumor cells plau in the development and growth of the subcutaneous tumor, and to evaluate histologically the metastatic rate. They transplanted 13,6 x 10^6, 13,6 x 10^4, and 13,6 x 10^2 tumor cells, respectively, to three groups of animals. With the first two doses, transplantation succeeded in 100% of cases, while with the last it was successful n 13,3% of males and 40% of females. The dose of transplanted tumor cells was found to be inversely proportional to survival, and proportional to the subcutaneous tumor growth. With the same dose of transplanted tumor cells, a significantly shorter survival and a smaller tumor bulk were observed in females as compared to males. Histological examination of all viscera except the brain showed the highest metastatic rate in the lung, kidney, suprarenal glands and pararenal lymph nodes. It was not influenced by the tumor dose or sex of the animal.