Bronchioloalveolar carcinoma of the lung (BAC) is a subtype of adenocarcinoma of the lung. Although traditionally grouped with other non-small cell lung carcinomas (NSCLC), BAC has unique morphological features and clinical behavior such as bilateral lung involvement, indolent course and lack of association with smoking. Some epidemiologic studies report a significant increase in the incidence of BAC. We used the SEER database to compare the incidence, demographics, and overall survival of BAC patients as compared to other NSCLC types over the past two decades (1979-1998). Although the incidence of BAC has increased over the past two decades, BAC represents less than 4% of all NSCLC in every time period evaluated. The 1 year survival rate is significantly better for BAC patients relative to other histological subtypes of NSCLC. There has not been a marked increase in the incidence of BAC reported to SEER over the past 20 years.