A retrospective study has been made of the long-term results of silastic replacement of the trapezium, including functional, clinical and radiological assessment of 43 hands, one to 13 years post-operatively. The results showed good function and relief of pain in 88% of hands. Radiolucent bone lesions, presumably due to silastic particle reaction, occurred in 53% of hands, but their presence did not correlate well with symptoms. Four patients (9%) developed significant synovitis which was improved by removal of the prosthesis. In this series, clinical silastic synovitis occurred in the first four years, and its incidence did not increase with further follow-up to 13 years.