Aqueous 1-butanol extracts were prepared from the ascites form of Gardner lymphosarcoma (LSG) maintained in C3H (H-2k) mice and from the solid Lewis lung carcinoma (LLCa) transplanted in B6 mice. C3H mice primed at least two times with cell surface antigens extracted from Gardner tumor cells (LSG-extract) lived longer than untreated controls if challenged with the solid Gardner lymphosarcoma cells. Tumors growing in immunized C3H mice differed from those growing in controls by shape, necrotization and inhibition of dissemination. If C3H mice were primed three times with LLCa extract then the survival was in comparison to intact controls prolonged only when the mice were pretreated into the site of tumor challenge. Survival time of B6 and B10 mice with transplanted LLCa was not markedly changed by previous priming injections of LSG-extract. An increase in mortality was recorded when LSG-extract-primed B10 mice were compared to the group of mice of the same line; similar effect has not been found in B6 mice.