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The average dermal ridge breadth in the second interdigital area was found to be significangly greater in an African Black sample than in the known Caucasian samples. Between race differences are roughly equal to within population sex differences, and are as great or greater than many of the differences observed between Caucasian controls and patients exhibiting sex chromosome aneuploidies. These race differences cannot be explained by differences in hand size or body size, so they apparently reflect developmental differences during the process of ridge formation.