Oral treatment of mice with Rasayanas (50 mg/animal/day for 5 days) was found to increase their immunological status as demonstrated by significant increase of total WBC counts and percentage of polymorphonuclear cells in the peripheral blood. The peak increase was obtained on day 6 (P<0.001). Administration of Brahma Rasayana also increased the life span of Dalton's lymphoma ascites tumor bearing animals by 42% (P<0.001). Moreover, there was a lag in the development of solid tumors produced in mice by Dalton's lymphoma ascites tumor cells when treated with Rasayanas.