The left hand of each of 903 white males, most of them well-educated professionals, was evaluated for osteoarthritis, in the ongoing Baltimore Longitudinal Study of the Gerontology Research Center. The results of the joint-digit prevalence study indicated that: 1) the prevalence of osteoarthritis varies from one digit to the other; 2) osteoarthritis is considerably more prevalent in the distal than the proximal interphalangeal joints, regardless of digit or age group; 3) this disease is not only more prevalent in the distal interphalangeal joints, but it usually appears in a more severe form in the distal than in the proximal interphalangeal or the metacarpophalangeal joints. 4) Assuming that the presence of osteoarthritis in one joint is independent of the presence of the disease in the other joint of the same digit, there is an excess of digits with osteoarthritis in both the distal and proximal interphalangeal joints. This is suggestive of either a common etiology or that the presence of the disease in one joint enhances the development of osteoarthritis in the other joint of the same digit.