Polymyositis/dermatomyositis are a heterogeneous group of diseases characterised by skeletal muscle inflammation and necrosis.' 2 Since an excellent clinical description in 1903 by Steiner of dermatomyositis, which is essentially still valid,3 much progress has been made towards our understanding of this group of diseases. The most widely used clinical classification of idiopathic inflammatory myopathies is the one proposed by Bohan and Peter in 1975.4 That was a landmark, providing guidelines in clinical practice to accurate diagnosis of inflammatory myopathies and standardisation of studies. Nonetheless, the classification was based on clinical data. In view of recent histological and immunological studies the classification proposed by Karpati et al in 1987 seems better to fit our current view of such diseases5 (table 1). In this review we focus on recent developments in polymyositis/dermatomyositis, analysing separately the currently considered third major form of inflammatory myopathy-inclusion body myositis.