Nine (2%) of 429 small-cell lung cancer (SCLC) patients seen at Vanderbilt University between 1977 and 1983 had a combined subtype SCLC at diagnosis (ie, small-cell carcinoma plus squamous cell or adenocarcinoma). Staging procedures and chemotherapy treatment were uniform for all 429 patients. The diagnosis of combined histology was established via bronchoscopy (six patients), needle aspiration biopsy (one), lymph node biopsy (one), and thoracotomy (one). The clinical characteristics of the combined subtype patients were similar to patients with other subtypes of SCLC (ie, there were no differences in median age, sex, performance status, and stage of disease). However, patients with a combined subtype histology had a higher incidence of peripheral lesions on chest x-ray (56% v 14%, P less than .001) and a lower median lactate dehydrogenase (LDH) (301 IU/L v 341 IU/L, P = .0002) at diagnosis. The overall response to chemotherapy (57% v 78; P = .5) and the median survival (8 months v 10 months; P = .4) of the combined subtype patients were similar to patients with other subtypes of SCLC. Two (22%) combined histology patients survived greater than or equal to 5 years. Both had had surgical resection in addition to chemotherapy. These data suggest that the combined subtype of SCLC is clinically similar to pure SCLCs and that surgery may play a prominent role in the management of these tumors. The possibility of a combined histology tumor should be considered in patients thought to have SCLC on the basis of limited biopsy material, such as a needle aspiration or bronchial biopsy, and when the primary lesion is peripherally located on chest x-ray.