A manifesting female carrier of Duchenne muscular dystrophy (DMD) with no prior family history of DMD is described. She presented with proximal muscle weakness, enlarged calf muscles and an elevated serum creatine phospokinase (CPK). Histological myopathic changes and immunoperoxidase examination for dystrophy in muscle biopsy with anti-dystrophin serum proved to be valuable in the diagnosis of DMD in a manifesting female carrier.