Sixty-four muscle biopsies obtained from patients with Duchenne muscular dystrophy, limb-girdle dystrophy, congenital muscular dystrophy, or who referred for diagnosis were examined with histochemical methods for dystrophin staining with antidystrophin antibodies. Six atypical cases in whom the dystrophin expression was inconsistent with both clinical and morphopathological pattern were selected: one case of Duchenne muscular dystrophy in whom dystrophin was partially represented, one case referred for investigation in whom dystrophin was absent, despite the lack of clinico-morphological signs supporting the diagnosis of Duchenne disease, two cases of congenital muscular dystrophy in whom dystrophin was absent and one patient with the same diagnosis in whom dystrophin was present, but quantitatively reduced. A patient with limb-girdle muscle dystrophy, in whom immunohistochemical investigation was necessary for the diagnosis is also reported. In conclusion, the immunohistochemical investigation using antidystrophin labelled antibodies of muscle biopsies obtained from patients with various types of muscular dystrophy is mandatory.