[Abstract] Objective To assess the role of a portable ultrasound device in the insertion of radial artery catheters. Methods Elective surgery 132 patients (ASA grades Ⅰ～Ⅱ) requiring arterial catheter insertion for intraoperative monitoring. A total of 132 patients requiring an arterial catheter were randomized to either the ultrasound (66patients) or palpation technique (66patients). The time taken from skin puncture to successful arterial catheter insertion, the time taken per insertion attempt, and the number of attempts required were recorded for each group. A portable ultrasound device was used to visualize the radial artery at the wrist and to direct arterial catheter insertion. This new technique of arterial catheter insertion was compared with the classic palpation technique. Results The arterial cannula was inserted on the first attempt in 39（63%） cases using ultrasound vs. 21（34%） cases by palpation (p<0.05). Significantly fewer attempts were required for catheter insertion using ultrasound as compared with palpation (mean±SD，1.6±2.0与3.1±2.4；p<0.05); however, the time taken for each successful attempt was longer (27.1±2.5与17.5±1.8 secs,p<0.05). The shorter overall time required for catheter insertion was found for the ultrasound group (55.6±63.9与112.5± 123.5 secs,p<0.05). There were four failures in the ultrasound group and four in the palpation group . Conclusion Ultrasound is a useful adjunct to radial arterial catheter insertion and increases the rate of success at first attempt. The technique is easy to learn and can reduce the time taken to insert the catheter.