We identified 29 bronchial washing, bronchoalveolar lavage, sputum, and fine-needle aspiration specimens with corresponding surgical pathology specimens with features of bronchioloalveolar carcinoma (BAC). Surgical pathology correlates were reclassified according to the 1999 World Health Organization classification into pure BAC, mixed adenocarcinoma-BAC (AD-BAC), and papillary adenocarcinoma (PAP-AD). Twelve cases of invasive pulmonary adenocarcinoma (INV-AD) without a bronchioloalveolar component were reviewed for comparison. The cytology slides were evaluated for 12 features of BAC. No statistically significant feature permitted separation of BAC from AD-BAC or from PAP-AD. However, comparison of BAC with INV-AD identified 9 statistically significant cytologic features: clean background, absence of 3-dimensional clusters, neoplastic cells in flat sheets, orderly arrangement of cells with round uniform nuclei, predominance of mucinous cells, absence of nuclear overlap, absence of irregular nuclear membranes, fine granular chromatin, and nuclear grooves that were features of BAC cases. Although cytologic evaluation cannot prospectively diagnose BAC, the bronchioloalveolar pattern may be recognized and suggests in situ proliferation that is present in BAC, AD-BAC, or PAP-AD. The bronchioloalveolar pattern must be correlated with clinical, radiographic, and histologic parameters to determine whether the tumor is localized, multifocal, or diffuse and whether there is parenchymal invasion.