Mitotic chromosome analyses performed on 820 infertile men revealed 60 (7.3%) men with some kind of chromosomal abnormality. Sex chromosomal abnormalities were detected in 28 (3.4%) and autosomal translocations in 9 (1.0%). Pericentric inversions of chromosome 9, with possible adverse effect on reproduction, was found in 23 (2.8%). Chromosome variants comprised a group of 77 (9.3%) subjects. We suggest that men with severe oligozoospermia and azoospermia should be considered for cytogenetical evaluation.