Several novel therapies for Duchenne muscular dystrophy (DMD) have recently been developed. However, steroids are currently the only medication that has been objectively confirmed to have an effect on muscle weakness in DMD patients. Prednisolone has recently been approved for pharmaceutical use in DMD patients in Japan. Moreover, the domestic guidelines for DMD have been published, which may lead to an increase in the use of steroid therapy. The short-term effects of steroid therapy for improving motor function have already been confirmed. Subsequently, the long-term effects of steroid therapy, such as prolonging the time until loss of walking ability, delay of scoliosis, and preservation of cardio-pulmonary function, have also been recognized. However, the long-term side-effects, such as obesity and bone demineralization, remain a concern. Several clinical studies are currently ongoing, worldwide, to develop an optimal regimen of steroid therapy.