Genetic factors have a major importance in male infertility etiology. Numerical and structural chromosomal abnormalities seem to be frequent inoligospermia and azoospermia cases with unknown etiology. In this study, 819 patients with azoospermia (383) and oligospermia (436) who attended the infertility department between 1995-2005 were evaluated. Spermogram and basic hormone proties (FSH-testosterone) were studied two times in a one month interval from each patient, and all the cases were evaluated cytogenetically. The 47 (12%) of 383 azoospermia patients and the 20 (4%) of 436 oligospermia patients were found to have chromosomal abnormalities. The 9 (19%) of the chromosomal abnormalities found in azoospermia patients were autosomal and the 38 (80%) were gonosomal. In oligospermia cases, the 8 (40%) of the chromosomal abnormalities were autosomal and 12 (60%) were gonosomal. Cytogenetic analysis and genetic counseling would be helpful in infertile males with azoospermia and oligospermia by determining the genetic factors causing infertility and by assessing the genetic risks of the offsprigs provided by assisted reproductive techniques.