We concur with the idea that congenital muscular dystrophy (CMD) is a distinct clinical entity, and report 17 patients (2 negroes and 15 whites; 12 M and 5 F; median age 6 years, range 1 to 24 years) with genetic, clinical, laboratorial, electrophysiological and histochemical studies. All our cases have an inheritance compatible with an autosomal recessive pattern. A decrease in fetal movements was reported by 57% of the mothers, generalized hypotonia at birth was present in 82%, limb girdle and neck weakness, absent or decreased deep tendon reflexes, and limb contractures were present in all. Severe muscular wasting was found in 41%. Calf pseudo-hypertrophy was observed in one patient. A patient was severely mentally retarded and another was borderline. During a 30-month follow-up, the muscle weakness of the majority remained essentially unchanged but the degree of motor activity deteriorated and was proportional to the worsening of the limb contractures. Serum CK levels were normal or increased to a maximum of 8 times. The electromyogram was myopathic in 74%, neurogenic in 13% and normal in 13%. CT scans showed a symmetrical white matter hypodensity in the hemispheres in 8 cases. All but 5 patients were operated upon to release the limb contractures and all were submitted to physical therapy. The contractures recurred in 4 patients submitted to surgery and were probably related to the cessation of physical therapy.