The purpose of this long-term, open parallel-group, double-consent study of alternate-day, low-dose prednisone in 2-4-year-old patients with Duchenne muscular dystrophy (DMD) was to determine whether prednisone produces a beneficial effect when given earlier than usual. Muscle function was evaluated by timed tests, and muscle strength with a hand-held myometer. After 55 months of treatment, the five patients (mean age 8.3 years) in the prednisone group were still able to get up from the floor, whereas two of the three in the control group had lost this ability. Side effects included a decline in growth rate in the prednisone-treated patients and excessive weight gain in one control and three treated patients. Because steroids are effective in prolonging function, but not in recovering lost function, we propose that treatment be started with low-dose prednisone in DMD patients as soon as the diagnosis is definite.