During a study of lung function in patients with systemic sclerosis, we followed 71 patients with this diagnosis for a mean of 5 years. During this period, 3 cases of lung cancer were observed in the group, giving a post hoc incidence of lung cancer of 8.6 cases/1000 persons/year compared to an expected incidence of 0.52 cases/1000 persons/year. The relative risk ratio for lung cancer in systemic sclerosis patients is 16.5. There was no definite association of lung cancer with cigarette smoking, but all 3 patients had either radiographic or pulmonary function evidence of interstitial pulmonary fibrosis. Although bronchoalveolar carcinoma is the most prevalent histologic type of lung cancer associated with systemic sclerosis in the reported cases in the literature, this was not present in any of our patients.