During a three years period, evaluation of etiologic factors in 385 consecutive infertile men revealed chronic prostato-vesiculitis as the commonest cause (25.7%) followed by varicocele (21.8%). In 77% of the patients with chronic prostatitis the authors found a decreased spermatozoa motility rate. AN obstruction of the sperm duct was found in 7,8%, autoagglutination in 5.7%. Idiopathic infertility was diagnosed in 10.9% of the patients. The significance of these findings and the contributions of other causes in this series are discussed.