A retrospective study of 21 hands in 19 patients was carried out to show the results after excision of the os trapezium for the treatment of arthrosis of the first carpometacarpal joint. A technically easy procedure was used that was based on a tendon plasty using the abductor pollicis longus (APL) tendon. Special attention was paid to the effects of compressive load on the stability of the thumb. The mean follow-up time was 25 months (range 11-38) and all patients achieved good mobility. Pain was reduced in all cases but one. In operated hands grip strength was 84% of estimated normal strength and pinch strength 83%. On radiographs of the hands the mean distance between the base of the metacarpal bone and the scaphoid bone was 4.6 mm, this was reduced by 1.9 mm during compression. When radiographs were taken during a compressive load, two dislocations of the thumb base were found that had otherwise been missed.