The first two cases of sporadic Duchenne muscular dystrophy (DMD) in females without a family history of DMD are reported. Both females had normal chromosomes and were identified as DMD by in vitro studies of protein synthesis by muscle ribosomes and by carrier studies of the mother of the proband. These observations are important for the genetic counselor. The possible diagnosis X-linked DMD has to be considered for every female with sporadic pelvifemoral MD, and carrier studies have to be requested for the proband's mother and possibly other maternal female relatives.