A technique for immediate interpretation of transbronchial aspirates at bronchoscopy is described. Comparing 73 aspirates using the technique with 134 routinely processed aspirates, the technique produced a significant increase in the percentage of specimens containing malignant cells, from 31 to 56 percent, and, importantly, a large decrease in the percentage of specimens that were inadequate for diagnosis, from 56 to 18 percent. The technique was equally applicable to central and peripheral lung aspirates and to all types of primary and metastatic pulmonary neoplasms. The use of rapid on-site evaluation significantly improves the diagnostic yield of transbronchial aspirates.