Retroperitoneal fibrosis has been observed in two patients with Parkinson's disease treated with bromocriptine. The patients complained of abdominal or lower back pain and presented with various degrees of renal insufficiency, with anuria in one. Laboratory evaluation furthermore showed an increased sedimentation rate and inflammatory anemia. Computerized tomography disclosed marked retroperitoneal thickening, and biopsy was performed in one patient. The symptoms appeared eighteen months and five years after treatment was started, at doses of 20 and 22.5 mg of bromocriptine daily. The medication was discontinued in both patients and steroid therapy was initiated, with resolution of all clinical, biological and radiological evidence of disease. This potential but rare complication of a widely prescribed drug warrants monitoring of renal function and sedimentation rate in patients undergoing bromocriptine treatment.