The histopathologic features of pulmonary lesions found in 36 patients with head and neck cancer ( HNC ) whose chest radiograms had abnormalities suggestive of a neoplasm were reviewed. Ten patients (28%) had benign lesions but cancer was diagnosed in 26 patients (72%) by lung biopsy or at autopsy. Second primary lung cancer was found in 19 (53%) and metastatic HNC in seven (19%) of the 36 patients examined. The second lung primaries occurred in seven (100%) patients with HNC in stage I or II and in 12 (63%) of those in stage III or IV. The histologic examination revealed squamous cell carcinoma of the lung in eight (42%) of 19 patients, small cell carcinoma in six (31.5%), adenocarcinoma in three (16%), and large-cell carcinoma in two (10.5%). These findings indicate that a prompt histologic examination of radiographically detected neoplastic pulmonary lesions in patients who have, or have had HNC is mandatory because a second primary cancer of the lung may be found and cured with early treatment. Furthermore, a substantial number of the patients in this retrospective analysis had small-cell carcinoma of the lung and could benefit from current therapeutic advances for this type of tumor.