The present investigation was desgined to evaluate the effects of melatonin on testosterone and pituitary hormones levels in mature male rats Twenty mature male rats were used in this study. Animal were divided into two groups each one consists of ten rats . The first group considers as contral group administrated soya oil (2ml / kg) , the second group treated with melatonin (0.5mg 1 kg) for one month . After the end of the experiment rats were sacrificed and blood was collected into heparinzed tubes to separate plasma and testicular tissue were collected to detect oxidive changes of the malenaldehyde (MDA) concentration and activities of superoxide dismutase (SOD) and catalase (CAT) . The results revealed that plasma level of testosterone and luteinzing hormones were significantly deceases (P ‹ 0.5) in melatonin treated group as compared with normal one , while reduces testicular concentration of MDA and increases the SOD and catalase activities . It was concluded that Melatonin has direct effects on testiculars and pituitary gland hormones and has antioxidant effects.