Biopsy material has proved to be of value in the investigation of many inflammatory and malignant disease processes. Examination of the synovial membrane by open biopsy, under anesthesia, has been performed by orthopedists for many years. Polley and Bickel, in 1951, 1,2 described an instrument for performing a closed punch biopsy. The purpose of this study was to determine the value of the closed punch biopsy procedure in an active outpatient arthritis clinic. The greatest potential value of a synovial biopsy in clinical practice would be to establish a diagnosis. In certain arthritic conditions, this is possible. If urate crystals are demonstrated in the synovial membrane, the diagnosis of gouty arthritis may be established. 3 Tuberculous arthritis and pigmented villous synovitis may also be accurately diagnosed by joint biopsy. Unfortunately, the histological changes in the synovial membrane of osteoarthritis, rheumatoid arthritis, "the collagen diseases," and traumatic and infectious arthritis, are