Radius, ulna, short bones (RUS) and carpal (CARP) bone age were assessed in 26 steroid-dependent nephrotic boys after at least 1 year of alternate-day prednisone therapy, and in 26 age- and sex-matched control subjects. No significant difference in RUS bone age was found between patients and controls. CARP bone age of patients was significantly (P = 0.01) more retarded than in controls. In patients, CARP bone age delay was related to their relative height at the time of study (P = 0.01). We conclude that CARP bones are more prone to effects of steroids than are RUS bones. Therefore, CARP bone age may be a more sensitive tool in monitoring the effects of steroids on skeletal growth and maturation.