Adenosquamous carcinoma of the lung is an uncommon form of the lung cancer. Owing to the infrequent occurrence of this disease, no series reported to date (and to our knowledge) has been of adequate size for definitive statistical analysis. In this study, survival curves and background factors affecting prognosis in those with resected adenosquamous carcinoma of the lung were reviewed. In the period from 1973 to 1994, a total of 1,284 patients with primary lung cancer, including 44 cases (3.4%) of adenosquamous carcinoma, were surgically treated in our department. The cumulative 5-year postoperative survival rate, for all cases of adenosquamous carcinoma of the lung was 18.5%. When the survival rates were compared by histologic type, the outcomes of patients with adenosquamous carcinoma were statistically worse than for patients with squamous cell carcinoma and adenocarcinoma, owing to the highly aggressive pathologic stage of adenosquamous carcinoma. The background factors most closely associated with the survival rate in those with adenosquamous carcinoma, using Cox's proportional hazard model, were gender and the degree of nodal involvement. Five-year survival was obtained in seven patients as follows: T1N0M0 in one patient, T2N0M0 in three, T2N1M0 in two, and T3N0M0 in one. Of these seven patients, all had received complete resections, and five were N0 cases. Although our series is small, this study suggest that adenosquamous carcinoma of the lung is an aggressive tumor that grows rapidly.