We reviewed the records of 251 patients whose cases were diagnosed between 1958 and 1978 at the Children's Hospital Medical Center Special Treatment Center for Juvenile Arthritis. We used a computerized system that included retrieval of data on range of motion, pain, joint swelling, functional capacity, and radiographic changes at each six-month visit over the years that the patient was followed. For the patients who were operated on, the radiographic information was evaluated preoperatively and at the last radiographic follow-up (average, six years after operation). The data bank contained postoperative radiographic information for thirty-two of the joints that had been operated on. We reviewed the late results of forty-one synovectomies in thirty children. The data included range of motion, swelling, and pain before operation, at one and two years after operation, and at an average of 7.1 years of follow-up. There were few if any benefits from the operation with reference to pain or improvement of range of motion, but it did seem to provide permanent relief of the joint swelling. Furthermore, radiographic deterioration seemed to continue in the joints that had been operated on if they already had radiographic changes at the time of operation (late synovectomy). In the joints without radiographic changes at the time of operation (early synovectomy), there seemed to be a continuation of deterioration in those affected by polyarticular disease, while the changes were less pronounced in those affected by pauciarticular disease. We undertook this study with a positive attitude toward synovectomy in the treatment of juvenile rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)