In contrast to the 15-20% incidence of the coexistence of acute dermatomyositis-polymyositis and malignancy, it has been accepted traditionally that the association of progressive systemic sclerosis, a disease with several features that may overlap the former condition, and malignancy is purely fortuitous. This experience has not been altered by the material presented in this review. However, the factual coexistence has been illuminated by a review of the pertinent literature and presentation of 12 previously unpublished case reports. Four cases concern pulmonary malignancies in PSS; eight are of an associated non-pulmonary malignancy. In the first group, the development of a malignancy superimposed on the chronic fibrosing changes in the lungs of PSS does not seem so strange, particularly in view of a possible immunologic reaction by collagen in considering pathogenesis. This immunologic process might be similar to a related immunologic process responsible for the development of malignant cells in pulmonary and other tissue, where normal cells usually are found. The high incidence of males is related to the high incidence of males in Veterans Administration Hospitals, the principal population source of these cases.