In a 36-month period, 240 patients at our institution received kidney transplants from cadaver donors. Cyclosporin A (CsA) was used as the initial immunosuppressive therapy. Seven patients (5 men and 2 women) developed severe pain, periarticular soft tissue swelling with no effusion, and vasomotor changes in affected areas. Although articular mobility was conserved, most of the patients had great difficulty in walking. A patchy osteoporotic pattern was seen radiographically and increased uptake of 99mtechnetium with a periarticular distribution in the clinically affected areas were found. All of these symptoms and radiographic and scintigraphic signs are compatible with definite reflex sympathetic dystrophy syndrome (RSDS). Articular symptoms began within 3 months after kidney transplantation in all patients; all but 1 patient had plasma CsA levels greater than 200 ng/ml at that time. When the dosage of CsA was reduced, there was concomitant improvement in the RSDS, which appeared when the plasma CsA levels declined to less than 200 ng/ml. The mean duration of the clinical symptoms of RSDS was 8 months. We believe RSDS should be added to the list of complications that may appear in kidney transplant patients who receive CsA treatment.