We report 21 patients (12 males and 9 females), belonging to 20 families with the clinical and laboratory features of a distal myopathy of Miyoshi type. The main clinical features of these patients were: (1) onset in late adolescence or early adulthood (mean age 20.3 years), (2) early and predominant involvement of the posterior compartment muscles of legs, (3) marked elevation of serum CK (mean value 4473 U/l). Only in one family were there two affected sibs. All other cases were sporadic and a consanguinity of parents was found in 4 cases. The evolution was progressive, but all patients except one remain ambulatory. Muscle biopsy showed a dystrophic pattern. Some of these patients were initially considered as having polymyositis; immunosuppressive therapy was always ineffective. In conclusion, the Miyoshi distal myopathy is not uncommon, but this disorder is often misdiagnosed.