The effects of gamma irradiation on germination, seedling height and survival rate of two sesame (Sesamum indicum L.) cultivars from Senegal were investigated. Seeds of the extensively grown cultivars in Senegal, "32-15" and "38-1-7", were irradiated with 0, 100, 200, 300, 400, 500, 600, 700 and 800 Gy. The irradiated seeds (0, 300 and 400 Gy) of a Turkish cultivar "Birkan" were also used as a reference. Irradiated seeds were sown with their respective controls both in field and greenhouse conditions to assess germination rate, seedling height and survival rate as affected by the different doses of gamma rays. Germination, seedling height and survival rate significantly decreased with increasing irradiation dose. The depressive effect of radiation on germination was more pronounced in the field than in the greenhouse conditions. Cultivar "32-15" was more sensitive to gamma irradiation than cultivar "38-1-7". The effective dose which caused 50 % growth reduction was 645 Gy for variety "32-15" and 740 Gy for variety "38-1-7". The lethal dose (LD50) determined at 50 days after sowing was 550 Gy and 740 Gy for "32-15" and "38-1-7", respectively. From the parameters studied, seedling height reduction or LD50 can equally be used in determining effective dose suitable for inducing artificial mutations.