BACKGROUND Anabolic-androgenic steroids (AAS) are abused by athletes. OBJECTIVE The present study was designed to evaluate chronic administration of high doses of nandrolone decanoate (ND) on the pituitary-gonadal axis and hematological parameters in normal male rats. METHODS Thirty Wistar-Albino male rats were divided assigned to control (C), placebo (P) and test (T) groups (n = 10). Group T received 15 mg/kg intramuscular (IM) ND for eight weeks. Group P received the same volume of peanut oil, but group C did not receive any agent during the trial period. At the end, animals were anesthetized, killed and blood samples collected from cervical vessels. Serum follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels were determined by sensitive rat gonadotropins kit, using ELISA methods. Serum testosterone and hematological parameters were measured by ordinary laboratory methods. Obtained data was analyzed using SPSS 17 by ANOVA and Tukey statistical tests. Results were expressed as Mean ± SD. Statistical difference considered significantly by P < 0.05. RESULTS Serum testosterone, LH, FSH, weight gain, food and water intake in group T were significantly decreased compared to other groups (P < 0.05). In addition erythrocyte, leucocytes, hemoglobin and hematocrit in group T were significantly increased compared to those of other groups (P < 0.05). CONCLUSIONS Chronic administration of high doses of ND can alter serum FSH, LH and testosterone and hematological parameters in male rats.