Open lung biopsies from 14 patients and autopsy tissue from one patient with polymyositis/dermatomyositis were reviewed in an attempt to correlate histologic features with clinical, radiographic, and prognostic variables. Three major groups based on histologic patterns were identified: bronchiolitis obliterans organizing pneumonia (BOOP), usual interstitial pneumonia (UIP), and diffuse alveolar damage (DAD). Patients with BOOP had a more favorable prognosis than did patients with UIP. Patients with DAD had a uniformly poor prognosis. One patient had a cellular interstitial pneumonia and did well. Histologic subclassification of the interstitial lung disease proved to be a better predictor of survival than did the radiographic appearance or the clinical presentation. These findings suggest that there is a broader range of histologic findings in polymyositis-dermatomyositis than is suggested in the literature and subclassification may be useful for prognosis.