Bronchioloalveolar carcinoma may present with a variety of radiologic and clinical patterns. Two types of this primary carcinoma of the lung have been recognized: a solitary lesion and a diffuse form. Charts and radiographs of 61 cases of bronchioloalveolar carcinoma were reviewed as well as the pertinent literature. Our experience indicates that the localized form seldom, if ever, becomes diffuse and has a good prognosis following appropriate surgery (lobectomy or pneumonectomy). If the lesion is diffuse, death almost invariably results within 3 years. Based on available clinical information, we suggest that at least two primary tumors of the lung have the histologic pattern of bronchioloalveolar carcinoma: one of these tumors is diffuse and the other is solitary.