Abstract: We present the first reported study of the effects of feeding Rhanterium epapposum aerial parts at 20, 50, 100 and 200 g kg-1 of standard diet to male Wistar rats for 12 weeks. The criteria of assessment of the plant toxicity were the effects on growth, organs of the body, hematological and serobiochemical parameters of rats. Depression in growth and hepatonephropathy were severe in rats fed diets containing 100 and 200 g kg-1 of R. epapposum aerial parts. These findings were accompanied by macrocytic hypochromic anemia, leukocytosis due to lymphocytosis and alterations of serum concentrations of urea, total protein, globulin and other serum constituents. Toxicity may be frequent in animals that ingest this plant in a dry year. While this plant has traditionally been used in Sudan and other Afro-Asian countries it may show toxic effects in human that result from over-dosage because, in general, there is no standardized dosage system in traditional medical practice.