Effects of Andrographis paniculata extract and its major component, andrographolide, on cell-mediated immune responses in metastatic tumor bearing animals were studied. NK cell mediated target cell lysis was enhanced by the administration of Andrographis paniculata extract (45.0% cell lysis) and andrographolide (40.2% cell lysis) on the 5th day after tumor induction when compared to untreated metastatic tumor bearing animals in which maximum target cell lysis was observed on 11th day (11.4%). Antibody dependent cell-mediated cytotoxicity (ADCC) was also enhanced by treatment with the extract (42.0% cell lysis) and andrographolide (40.2%) in comparison with the untreated case (11.0%). Similarly, the extract (25%) and andrographolide (22%) showed higher ACC activity than the control (14%) and treatment of extract and andrographolide resulted in significant increase in serum IL-2 and TIMP-1 levels. Furthermore, the levels of proinflammatory cytokines such as IL-1ß, IL-6, GM-CSF and TNF-α were effectively reduced by the administration of extract and andrographolide in metastatic tumor bearing animals.