Seven unrelated women were manifesting carriers of Duchenne muscular dystrophy. A manifesting carrier of Duchenne muscular dystrophy is defined as a female with a history of Duchenne muscular dystrophy in her pedigree who has symptomatic weakness. All were characterized by slowly progressive weakness that began in the second or third decade of life. Asymmetric weakness was present in only three of the seven patients. Serum creatine kinase values were elevated in all patients and none had an electrocardiogram indicating ventricular hypertrophy. The electromyogram and muscle biopsy specimens were reported as myopathic in all patients studied. In the absence of a male relative with Duchenne muscular dystrophy, clinical distinction from cases of autosomal recessive limb girdle muscular dystrophy may not be possible. The development of new techniques in molecular genetics should allow precise identification of manifesting carriers of Duchenne muscular dystrophy in the near future.