Oral administration of lambda in a doses of 1.6 and 4.0mg/kg b.wt. daily for 65 successive days Significantly decreased the weight of sexual organs, sperm cell concentration, sperm motility and the percentage of seminiferous tubules containing Spermatozoa while, the sperm abnormalities were increased. Moreover, the red blood cells, packed cell volume and haemoglobin concentralions were decreased while, the white blood cells were increased due to the neutrophilia and lymphopenia. The level of testosterone was not changed. The residual pattern of lambda in liver and muscle was also detected.