The expression of bcl-2 seems to influence the biologic activity of a variety of neoplasms. In this study, we examined bcl-2 protein expression in 47 surgically resected adenocarcinomas of the lung to determine its expression in the neoplastic and adjacent non-neoplastic cells. Seven squamous cell carcinomas, six small cell carcinomas, five non-neoplastic lung lesions, and five normal lungs were also studied. The bcl-2 protein was detected after antigen retrieval with bcl-2 monoclonal antibody using archival formalin-fixed, paraffin-embedded tissue material. Fifty-one of 52 cases had bronchioles that could be evaluated and all expressed bcl-2, and of these, 12 showed basal immunostaining, 17 showed luminal immunostaining, and 22 showed immunostaining in both cellular compartments. Thirty of the 47 adenocarcinomas expressed bcl-2, whereas four of seven squamous cell carcinomas and all six small cell carcinomas were bcl-2 positive. bcl-2 immunostaining was correlated with a survival using the Fisher exact test. There were no statistically significant differences in survival between patients with bcl-2-positive and bcl-2-negative adenocarcinomas (P = 0.332). Similar results were obtained using the Kaplan-Mier product limit survival analysis method (P = 0.356). Our study also showed that expression of bcl-2 is common in pulmonary adenocarcinomas and that bcl-2 expression may be found in the basal and the luminal surfaces of normal bronchioles.