A device designed to augment venous filling by applying a vacuum to the arm during tourniquet application was evaluated in adult patients considered to have difficult peripheral venous access and in need of nonemergent venipuncture or intravenous cannulation. Patients taking medications that affected platelet activity or who had venipuncture attempts within 1 week in the same extremity were excluded. A total of 21 patients (age, 38.8 +/- 15 years; weight, 77.3 +/- 22.5 kg) were studied. The majority were obese (62%) and/or did not have prominent veins even when a standard tourniquet cuff was placed (71%). Use of the device was successful in 19 patients (90%), with a mean time to venipuncture after vacuum removal of 38 +/- 30 seconds. In the 2 patients in whom the device was unsuccessful, both patients were intravenous drug users and subsequently required either external jugular or central venous line placement. Seven patients had unsuccessful attempts at venipuncture or intravenous cannulation on the opposite extremity immediately before use of the device. In these 7 patients, subsequent use of the device was 100% successful (p = 0.0003, Fisher's exact test, assuming all attempts using standard techniques would have been unsuccessful). When conventional tourniquets are unsuccessful for venipuncture, the use of the venous distension device may obviate the need for more invasive forms of venous access.