Clinicopathological, immunohistochemical and biochemical studies were performed on seven patients from five families showing an abnormal accumulation of desmin in the muscle fibers. Late onset myopathy was observed in all the cases studied. The clinical features were heterogeneous and usually nonspecific. However, some patients presented with dysphonia, dysphagia or cardiomyopathy. These features are highly suggestive of desmin myopathy. Using electron microscopy, desmin myopathy is characterized by an accumulation of granulofilamentous material. Depending on the distribution of the material, however, three different patterns of desmin accumulation can be observed: (1) large circumscribed inclusions, (2) intermyofibrillar areas of diffusely distributed material, and (3) deposits around large spheroid bodies. The second pattern is characterized by a rubbed-out appearance using oxidative enzyme reactions. For all the patients studied here, the immunohistochemical data showed that the desmin accumulation fitted these three patterns of distribution. For six patients, immunoblot analysis confirmed the desmin accumulation patterns and showed that an increase in the expression of the 53-kDa protein had occurred. The third pattern of desmin accumulation confirms the pathological heterogeneity of cytoplasmic and spheroid bodies. Desmin does not accumulate in all cytoplasmic and spheroid body myopathies, as observed in two other familial cases presented here.