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The palmar a-b ridge counts have been investigated in a series of 51 Japanese patients with Klinefelter’s syndrome. The mean total a-b ridge count was determined to be 72.51 in these patients, which did not differ significantly from mean counts obtained in normal Japanese male and female controls. It follows that the a-b ridge counts of Klinefelter’s syndrome among the Japanese are not as remarkably low as reported earlier.The palmar a-b ridge counts of Japanese victims of this congenital anomaly (47,XXY) are low as compared with White patients, possibly due to racial differences of a-b ridge counts between the Japanese and White populations.