Chromosomal analysis was performed on 109 males with teratozoospermia. Four cases of anomaly were found, including three cases of mosaic Klinefelter's syndrome and one balanced autosomal translocation. Among chromosomal heteromorphisms, 9qh+ was found in 25% of the patients. The fraction of malformed spermatozoa in the semen of the 9qh+ group is significantly higher than in the chromosomally normal group. It is speculated that heterochromatic variants like 9qh+ could be one of several unknown factors disturbing normal gametogenesis.