Growth and metastasizing of Lewis lung carcinoma were accompanied by complex changes in tumor sensitivity to cisplatin. On day 17 of growth, tumor sensitivity was much lower than immediately after transplantation. Further growth of Lewis lung carcinoma was accompanied by a progressive increase in its sensitivity to cytostatic treatment. The study of migration activity of the tumor and dynamics of metastasizing showed that metastatically active carcinoma cells dominated on day 17 of tumor growth, but then the number of these cells progressively decreased to the 29th day of tumor growth. Growth-related changes in the sensitivity of Lewis lung carcinoma were probably due to complex variations in the number of metastatically active tumor cells with high resistance to cisplatin.