Out of a population of 97 haemodialysis patients, 36 patients with dialysis arthropathy were identified. Dialysis arthropathy is a chronic symmetrical polyarthritis which affected 97 per cent of the patients who had been undergoing cuprophane haemodialysis for more than 10 years. It commonly affected the shoulders, hips, hands, knees and wrists, worsening with time and extending to other joints. Fifty-eight per cent of the patients complained of morning stiffness and 47 per cent complained of exacerbation of shoulder pain during or after haemodialysis. Half of the patients also suffered from carpal tunnel syndrome, which recurred and was associated with a long-lasting disability. The most common radiological abnormality was periarticular bone cysts, followed by articular erosions and a destructive spondyloarthropathy, but clinical symptoms were more common than radiological signs. Patients with dialysis arthropathy had a higher C-reactive protein level than patients without arthropathy (18.6 mg/l versus 11.4 mg/l), indicative of an inflammatory process. Some of the clinical manifestations of the disease correlated with levels of C-reactive protein and ferritin. Serum ferritin levels correlated strongly with the units of blood transfused in the past five years (RS = 0.83), and the logarithm of ferritin level correlated weakly with C-reactive protein (r = 0.32). Haemarthroses were documented in 19 per cent of patients. Mean serum beta 2-microglobulin was elevated in the patients with (57.3 mg/l) and without arthropathy (50.7 mg/l), and there was no difference in the parathormone or aluminium levels between these groups. Articular tissue was obtained in 25 patients; beta 2-microglobulin amyloid was present in 24. Larger deposits were present in the capsular tissue, and these appeared to replace collagen bundles in eight cases. Amyloid deposits replaced the lining layer in six cases. It is likely therefore that amyloid disrupts normal joint function by replacing normal joint tissue. Mild chronic synovitis with haemosiderin deposition were found in approximately 60 per cent of cases. These findings suggest that amyloid derived from beta 2-microglobulin has a primary role in the pathogenesis of dialysis arthropathy, but there was also evidence of inflammatory processes. It is suggested that iron overload or haemarthroses might contribute to the inflammation, but other factors, such as dialysis-related bioincompatibility reactions, may also have a role.