30 consecutive adult patients presenting with trigger thumb (31 thumbs) were entered prospectively into a study to determine the natural history of the condition. Five patients insisted on treatment and could not be followed to resolution, but the rest resolved spontaneously after an average duration of symptoms of 6.8 months (range 2-15). There was a small but non-functional reduction in movement of the thumb in some of the patients: six lost an average of 7 degrees of abduction and ten had an average loss of opposition of 1.4 (Kapandji grade). The remaining patients made a full recovery.