Osteoarthritis is the most ubiquitous rheumatic disease worldwide. Although its prevalence in various populations has been well documented, few studies have evaluated the longitudinal radiographic progression of the disease, especially as it is expressed in the interphalangeal joints of the hand. In this longitudinal study, left hand-wrist X-rays of 386 white male participants of the Baltimore Longitudinal Study of Aging followed for at least 5 years with two or more visits were examined for prevalence and progression of osteoarthritis of the distal and proximal interphalangeal joints of the hand. As other studies have shown, we found that the prevalence of osteoarthritis in both distal and proximal interphalangeal joints becomes progressively higher as the age of the subjects increases. Using the life table method of analysis we studied the progression of osteoarthritis as defined by the following criteria: (1) an increase in the severity of radiographic changes of the joints previously affected and (2) an increase in the number of new joints affected. The results indicated that osteoarthritis in both the distal and proximal interphalangeal joints progresses at a faster rate in the older population than in individuals less than 60 years of age. Furthermore, osteoarthritis in the interphalangeal joints progresses at the same rate whether the starting point was a Kellgren grade of 0 (no disease) or 1 (doubtful). We therefore conclude that grade 1 is an intermediate step in the inexorable progression of osteoarthritis of the interphalangeal joints and not synonymous with grade 0, as it has been customarily interpreted.