The work capacity of 26 women after a Chiari pelvic osteotomy for symptomatic unilateral subluxation of the hip was assessed using two simple exercise tests: the maximal walking speed during a 12-minute test and the time taken to climb stairs. A significant linear decline in walking speed occurred with increasing age, despite the operation, and only one patient over the age of 25 years was able to walk at a normal rate. Compared to the results in a control group of women of similar age the stair climbing time was increased in 54 per cent of the patients and showed a significant negative correlation with the maximal walking speed. Age-adjusted walking speed was closely associated with the degree of pain experienced but there was no relationship between observed function and conventional clinical assessment based on the range of movement and the radiographic appearances of the hip.