This study compared the modified BronchoCath double-lumen endotracheal tube with the Univent bronchial blocker to determine whether there were objective advantages of one over the other during anesthesia with one-lung ventilation (OLV). Forty patients having either thoracic or esophageal procedures were randomly assigned to one of two groups. Twenty patients received a left-side modified BronchoCath double-lumen tube (DLT), and 20 received a Univent tube with a bronchial blocker. The following were studied: 1) time required to position each tube until satisfactory placement was achieved; 2) number of times that the fiberoptic bronchoscope was required; 3) frequency of malpositions after initial placement with fiberoptic bronchoscopy; 4) time required until lung collapse; 5) surgical exposure ranked by surgeons blinded to type of tube used; and 6) cost of tubes per case. No differences were found in: 1) time required to position each tube (DLT 6.2 +/- 3.1 versus Univent 5.4 +/- 4.5 min [mean +/- SD]); 2) number of bronchoscopies per patient (DLT median 2, range 1-3 versus Univent median 3, range 2-5); or 3) time to lung collapse (DLT 7.1 +/- 5.4 versus Univent 12.3 +/- 10.5 min). The frequency of malposition was significantly lower for the DLT (5) compared to the Univent (15) (P < 0.003). Blinded evaluations by surgeons indicated that 18/20 DLT provided excellent exposure compared to 15/20 for the Univent group (P = not significant). We conclude that in spite of the greater frequency of malposition seen with the Univent, once position was corrected adequate surgical exposure was provided. In the Univent group the incidence of malposition and cost involved were both sufficiently greater that we cannot find cost/ efficacy justification for routine use of this device.