Patients with rheumatoid arthritis, psoriatic arthritis, and osteoarthritis were assessed by clinical evaluation, radiography, and joint scintigraphy using technetium labelled methylene diphosphonate (MDP) and technetium labelled liposomes. Although both scanning techniques were more sensitive than radiographs in detecting joint disease, the liposomes scans were positive only in clinically active inflammatory disease. In patients with rheumatoid arthritis liposome scintigraphy was also able to discriminate between different grades of joint tenderness. In inactive inflammatory polyarthropathies, although the MDP bone scans continued to show increased activity, the liposome scans did not and were therefore a more accurate reflection of the clinical state. The increased uptake in the liposome scans may be due to incorporation of the liposomes into the phagocytic cells of the synovium. This scan may, therefore, by reflecting the activity of cells involved in the disease process, provide a useful way of assessing disease activity and progression.