Extract of Tinospora cordifolia has been shown to inhibit the lipid peroxidation and superoxide and hydroxyl radicals in vitro. Concentration needed for 50% inhibition was 6 mg and 12.5 mg/ml, respectively. The extract was also found to reduce the toxic side effects of cyclophosphamide administration (25 mg/kg b.wt, 10 days) in mice hematological system by the free radical formation as seen from total white blood cell count, bone marrow cellularity and alpha-esterase positive cells. Moreover, administration of the extract partially reduced the elevated lipid peroxides in serum and liver as well as alkaline phosphatase and glutamine pyruvate transaminase. This indicates the use of Tinospora extract in reducing the chemotoxicity induced by free radical forming chemicals.