BACKGROUND The incidence of bronchioloalveolar carcinoma of the lung (BAC), a pathologically distinct type of nonsmall cell lung carcinoma (NSCLC), appears to be rising. In this study, the authors compared data on the clinical presentation and clinical courses of patients with Stage IIIB and IV BAC with data on other types of NSCLC. METHODS The authors collected clinical, radiographic, and pathology information about 28 patients with Stage IIIB and IV BAC and 124 patients with other histologic types of NSCLC. RESULTS Twelve of 28 BAC patients (43%) were women, compared with 40 of 124 control patients (32%). Nine (32%) of the patients with BAC had never smoked cigarettes, versus 20 controls (16%) (P = 0.02). Eighteen patients (64%) with BAC had bilateral multilobar or multicentric pulmonary involvement, compared with 13 controls (15%) (P < 0.001). Patients with advanced stage (IIIB and IV) BAC had a median survival of 15 months from the time of diagnosis; for patients with other types of Stage IIIB and IV NSCLC, had a median survival of 10 months (P = 0.01). CONCLUSIONS Patients with BAC of the lung have clinical, radiographic, and pathologic characteristics that distinguish them from patients with other types of NSCLC. A greater proportion of women and nonsmokers present with BAC than with other types of NSCLC. Patients with advanced stage BAC are more likely to have bilateral diffuse pulmonary involvement, are less likely to develop brain metastases, and have longer survival than patients with other types of Stage IIIB and IV NSCLC. Further research is warranted to define etiology, molecular abnormalities, and more effective therapeutic interventions. Cancer 1999;86:1165–73. © 1999 American Cancer Society. Patients with advanced bronchioloalveolar carcinoma of the lung are more likely to have bilateral pulmonary involvement, are less likely to develop brain metastases, and have longer survival than patients with other forms of advanced nonsmall cell lung carcinoma.