In recent years, progress has been made in the clinical description and delineation of neuromuscular diseases manifest primarily by skeletal muscle weakness. However, accurate diagnosis in the early stages before the development of advanced muscle involvement is still difficult. It is now recognized that a well-rounded symptomatic treatment program can help in preventing unnecessary complications and in obtaining maximal function from the residual musculature. Such a program will be most effective if efforts are directed early in the disease not only toward physical therapy and orthopedic modalities but also toward the psychologic reactions of these patients.1 There is a need for laboratory assistance not only in diagnosis but for long-term management as an aid in establishment of prognosis, evaluation of therapeutic effects, and as a guide in setting reasonable goals. Laboratory tests, which have been used in the past, such as urinary creatine and creatinine, reflect the amount of