Introduction Polymyositis is the most frequently occurring primary myopathy in adults and is second only in over-all incidence to the group of muscular dystrophies. The early accurate diagnosis of polymyositis is most important because this is the one type of primary myopathy for which potentially satisfactory drug treatment is available.1-7 It is presently felt that the corticosteroids are the most useful form of treatment, but the details of initial dosage, subsequent titration, and maintenance dosage have not been well described in the literature except in general terms which frequently do not provide sufficient guidance for rational therapeutic management. Indeed certain authors have concluded that corticosteroids may not be useful in treating polymyositis.8-10 Conflicting opinions concerning the efficacy of corticosteroid therapy have occurred because adjustment of dosage regimens in the past was often empirical without correlation with disease activity. The suggested treatment schedules have varied widely, not only in