A study was carried out to determine whether males contribute to repeated early pregnancy loss. Semen samples were analyzed from proven-fertile men (n = 51 group I) and from men whose partners presented with early pregnancy loss (>3 first trimester abortions, n = 32 group II). Routine analysis, sperm function tests, and ultrastructural studies of sperms were carried out. Female factor could be identified in 25 (78%) couples, and in 7 (22%) no cause either male or female could be identified and the semen analysis was normal. Percent morphologically normal did not differ significantly between the groups, but increased sperm head abnormalities were seen. The functional tests were all normal except for a significant decrease in the capacity of nuclear chromatin to decondense in vitro. The ultrastructural studies showed defects of chromatin condensation and irregular nuclei with vacuoles. This study points to the loss of chromatin integrity as a possible contributing factor from males to early pregnancy loss.