Major drawbacks of chemotherapeutic agents are their toxic side effects and lack of tumor specificity. Immunological and biochemical studies were here carried out to investigate protective effects of ethanolic extract of Andrographis paniculata against cyclophosphamide (CTX) induced toxicity in vivo. Intraperitoneal administration of the extract significantly increased the total WBC account (3256.5+/-196 cells/cm(2)), bone marrow cellularity (17.1+/-10.4x10(6) cells/femur) and betaesterase positive cells (849+/-23.2 cells/4000 cells) in CTX treated animals, when compared to CTX alone treated control mice. Weights of lymphoid organs such as a spleen and thymus, reduced by CTX administration, were also increased by A paniculata treatment. Reduction of GSH in liver (4.8+/-0.21nmol/mg protein) and in intestinal mucosa (13+/-0.67 nmol/mg protein) of CTX-treated controls was significantly reversed by A paniculata administration (liver: 6.4+/-0.13, intestinal mucosa: 17.11+/-0.06), with amelioration of changes in serum and liver ALP, GPT, LPO (lipid peroxidation). Histopathological analysis of small intestine also suggests that extract could reduce the CTX induced intestinal damage. The level of proinflammatory cytokine TNF-alpha, which was elevated during CTX administration, was significantly reduced by the A paniculata extract administration. The lowered levels of other cytokines like IFN-gamma, IL-2, GM-CSF, after CTX treatment were also found to be increased by extract administration.