Genetic studies have shown that the dominant gene for polledness found in the Saanen breed will, when homozygous, lead to pseudohermaphrodism, testicular hypoplasia or epididymal sperm granuloma and to an abnormal sex ratio (excess of males). An analysis of chromosomal constitution and nuclear appendages in peripheral leucocytes and tissue cultures of 17 pseudohermaphrodites, 10 males with epididymal sperm granuloma and 3 males with testicular hypoplasia was carried out. Sex chromatin could not be unequivocally distinguished in buccal or urinary bladder smears owing to the presence of other large chromatin masses. In no case was any trace of ovarian tissue found. One pseudohermaphrodite was a blood chimaera (XX/XY). This animal, a typical freemartin, was indistinguishable in anatomy or histology from the other pseudohermaphrodites. The chromosomal constitution and nuclear appendages of the remaining 16 pseudohermaphrodites and of the males with testicular hypoplasia were those of a genetic female. It is concluded that the pseudohermaphroditic effect of the polled gene is limited to genetic females and that males with testicular hypoplasia are actually genetic females showing an extreme pseudohermaphroditic effect. The abnormal sex ratio characteristic of the Saanen breed is thus shown to be a trivial consequence of classifying extreme pseudohermaphrodites as males. The chromosomal constitution and nuclear appendages of the males with epididymal sperm granuloma were those of a normal male. Hence the genetic factor for polledness, when homozygous in genetic males, can lead to the development of epididymal sperm granuloma.