The natural history of hand osteoarthritis (OA) is poorly understood. The aim of the study was to ascertain the extent and pattern of radiological progression of hand OA over a 10-year period. A follow-up study was carried out on 169 consecutive patients who initially presented with OA of the hands or knees between 1975-1977. Fifty-nine subjects (45 women and 14 men) were recontacted who had paired hand radiographs, a mean of 10 years apart, and were a mean 69 (range 53-86) years old at follow-up. X-rays were scored blind, in three joint areas--distal and proximal interphalangeal joints (DIP and PIP) and first carpo-metacarpal (CMC) joints--using the method of Kellgren and Lawrence (K&L) (0-4), and for osteophytes and narrowing (0-3). Using the highest score for right and left hands (N = 118), K&L changes at the three areas were similar with 47-50% deteriorating, 45-46% unchanged, and 6-8% improving. Similar deterioration was seen when scoring the three joint areas for osteophytes (38-39%) and narrowing (39-48%). New osteophytes appeared in 48% of DIP joints during the 10 years. There was a weak correlation between progression at the DIP and PIP joints, but no relationship between DIP and CMC, or CMC and PIP. Virtually all subjects (97%) deteriorated when the total scores of all joints were calculated. No significant differences were seen between 'severe progressors' and 'minor' in terms of age or body mass index (BMI). A nonsignificant increase in the proportion of knee progressors in the severe progressor hand group was seen and there was a higher rate of baseline DIP OA in knee progressors. These results suggest that the majority of patients with OA of the hands attending a rheumatology outpatients clinic deteriorate radiologically over a 10-year period, about half developing new changes in DIP joints. There were no obvious features distinguishing those with rapid deterioration, although DIP OA appears to be a risk factor for knee progression.