We conducted a randomized, controlled trial to prospectively confirm that ultrasound-directed transbronchial needle aspiration (USTBNA) results in: (1) improved sensitivity for detecting lymph nodes involved with neoplasm, and (2) a decreased number of aspirates needed to achieve a diagnosis as compared with standard transbronchial needle aspiration (TBNA). The study was conducted in a tertiary medical center on patients undergoing fiberoptic bronchoscopy in the evaluation of enlarged mediastinal lymph nodes. USTBNA or TBNA were followed by rapid, on-site cytopathology examination of the collected specimens. Measurements included the (1) age and sex of the patient, prior diagnosis of cancer, nodal short-axis diameter and node location as determined by computerized tomography (CT), and endobronchial abnormalities at bronchoscopy; (2) number, order, and location of transbronchial aspirates and results of on-site evaluation; (3) results of surgical exploration in patients with negative transbronchial needle aspiration; (4) sensitivity, specificity, and diagnostic accuracy of USTBNA and TBNA; (5) number of aspirates required for successful lymph node aspiration as well as for a diagnosis of cancer for both USTBNA and TBNA; and (6) multiple logistic regression analysis to determine the significance of combinations of clinical predictors and needle aspirate results. Eighty-two bronchoscopic examinations were performed on 80 patients. We found no significant difference between USTBNA and TBNA in sensitivity (82.6% versus 90.5%, respectively), specificity (100% for both), or diagnostic accuracy (86.7% versus 91.7%, respectively). The sensitivity, specificity, and diagnostic accuracy of USTBNA and TBNA were similarly high, regardless of node location (paratracheal or subcarinal). A decrease in the number of aspirates required for lymph node sampling approached statistical significance for all USTBNAs as compared with TBNAs (2.03 +/- 0.19 versus 2.62 +/- 0.25, p = 0.06), but this was not demonstrated for the number required to confirm cancer (1.95 +/- 0.47 versus 2.68 +/- 0.21, p = 0.17). The number of aspirates to successful lymph node aspiration decreased with USTBNA versus TBNA in paratracheal lymph nodes (2.00 +/- 0.20 versus 2.91 +/- 0.34, p = 0.03), but not to a diagnosis of cancer (1.93 +/- 0.25 versus 3.00 +/- 0.58, p = 0.11). No difference was seen in the number of aspirates for subcarinal nodes. The number of TBNA attempts for paratracheal lymph node sampling was inversely correlated with node size (r = 0.48, p = 0.02). No such relation was seen with USTBNA of paratracheal nodes (r = 0.09, p = 0.66), TBNA of subcarinal nodes, or USTBNA of subcarinal nodes. A similar relation was seen between the number of aspirates to a diagnosis of cancer. On multiple logistic regression analysis, a positive transbronchial aspirate was associated only with a larger lymph node and history of prior cancer. We conclude that: (1) in the setting of on-site cytopathology, transbronchial needle aspiration has a high sensitivity, specif...