A monocentric and submetacentric Y/Y translocation without evidence of mosaicism was observed in a male with tall stature and azoospermia. Chromosome measurements of the abnormal Y of this patient and the normal Y of his father were undertaken to determine more precisely the chromosome break points in this translocation. The measurements failed to show a definite loss of chromatin from the original short arm of the proband’s Y chromosome. The azoospermia and infertility in our patient, in contrast to his father, suggest that infertility may be associated with this specific Y/Y translocation in human male