Key words:Withania somnifera, lethal dose fifty, sub chronic toxicity, ashwagandah Withania somnifera (WS) has a wide range of therapeutic applications for several disorders. Toxicity studies on WS are very limited. The purpose of the present work was to study the acute and sub-chronic toxicity of WS extracts in rats and to determine the LD 50 value, which in turn helps in determining the dose range for the plant extract to be used with no harmful or lethal effects on the animal. Rats in acute study were IP injected with the alcoholic extract of WS (the aerial parts) at doses of (0), 150, 300, 600 and 1200 mg/kg bwt. In subchronic toxicity study WS extract was administered IP at a dose of 10%, 20% and 40% of the obtained LD 50 (52 mg/kg bwt, 104 mg/kg bwt and 208 mg/kg bwt respectively) for 60 days. Acute toxicity revealed an IP LD 50 of 522 mg/kg wt. Significant changes in body weight, hematological, biochemical and histopathological changes were recorded in 20% and 40% LD 50 groups with 15 -40 % mortalities respectively, by the end of the experiments. Based on this study, WS showed toxicity at doses higher than 10% LD 50 when given IP and it was suggested to use ≤ 10% LD 50 (IP) doses of WS extracts, than the tested here to start with in setup protection or treatment studies.Correspondence to: Khaled M.Ashry : ashrykh@yahoo.com