The effect of Punarnavine on the immune system was studied using Balb/c mice. Intraperitoneal administration of Punarnavine (40 mg/kg body weight) was found to enhance the total WBC count on 6(th) day. Bone marrow cellularity and number of alpha-esterase positive cells were also increased by the administration of Punarnavine. Treatment of Punarnavine along with the antigen, sheep red blood cells (SRBC), produced an enhancement in the circulating antibody titer and the number of plaque forming cells (PFC) in the spleen. Maximum number of PFC was obtained on the 6(th) day. Punarnavine also showed enhanced proliferation of splenocytes, thymocytes and bone marrow cells both in the presence and absence of specific mitogens in vitro and in vivo. More over administration of Punarnavine significantly reduced the LPS induced elevated levels of proinflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6 in mice. These results indicate the immunomodulatory activity of Punarnavine.