Previously untreated patients with small cell carcinoma of the lung (SCCL), who were treated at the Medical College of Wisconsin with combined chemotherapy and radiation therapy, were retrospectively subtyped according to the 1981 World Health Organization Lung Cancer Classification. Of 54 evaluated patients, 27 (50%) had "oat cell" subtype, 22 (41%) "intermediate cell" variety, and five (9%) were classified as "combined" type. There was no significant difference in response to therapy or median survival between the subtypes. In addition to the absence of prognostic significance among the subtypes, there were many technical factors affecting accuracy of subtyping, including tissue-crushing artifacts, size of biopsy materials, fixation of tissue samples, and variation of subtypes within the same biopsy. We conclude that subtyping of SCCL should not be construed as a prognostic tool or guideline to therapy. However, the recognition that SCCL may manifest in a variety of histologic patterns, some of which may be misinterpreted as a histology other than SCCL, is probably more important for choice of therapy and prognosis than the individual subtypes.