Fluorescent (F) body distribution was determined in a group of men who did not have a fertility problem, but rather had fathered exclusively female offspring. The study was designed to analyze spermatozoa for the frequency of zero F-body (X-bearing) and one F-body (Y-bearing) spermatozoa. Semen samples were separated (processed) for Y-bearing spermatozoa enrichment and reanalyzed for fluorescent body distribution. The study consisted of 50 control (10 males) samples (unprocessed), 35 preseparation (35 patients) samples (unprocessed), and 18 postseparation (18 patients) samples (processed). A significantly higher frequency (P less than 0.05) of zero F-body spermatozoa were observed in the preseparation samples when compared with the control samples. The presence of more spermatozoa without fluorescent body correlates with the occurrence of more female births.