Abstract: The study was designed to investigate the subacute toxicity, in vivo antioxidant and antitumor activity of aqueous ethanol extract of Senna alata on bearing carcinomaous cells. The results of the evaluation of the toxicity on albinos Wistars rats showed no death of rats and the increase of their weight after 26 days of administration of the extract. The liver enzymes activity alanine amino transferase (ALT), aspartate amino transferase (AST) and alkaline phosphatase (ALP) did not varied significantly as well as the concentration of creatinine of the treated rats both in the liver homogenate and serum compare to the control. The study was extended to the evaluation of in vivo antitumor activity of extract of S. alata on bearing carcinomatous cells on Nude mice. The results showed that after treatment with the extract at 100 and 200 mg kg-1 body weight, the levels of MDA decreased significantly (3.44 ± 0.76-1.97 ± 0.48) while the concentration of glutathione and the activities of CAT and SOD increased significantly. The results suggest that the aqueous ethanol extract of S. alata is not toxic and exhibits significant antitumor and antioxidant effects on bearing carcinomatous cells.