A retrospective study of 431 patients who had peripherally inserted midclavicular or central catheters placed during a consecutive 13-month period using the conventional landmark method for placement was compared with a second group of 326 patients, who during a 12-month period had such catheters placed using ultrasonography. The data demonstrate a 42% decrease in the number of needle penetrations needed to successfully cannulate veins when ultrasound was used during placement. There is a 26% greater chance of successful cannulation of the vein on the first attempt with ultrasound-guided placements than with those using the traditional landmark method.