Percutaneous radial artery cannulation is a well-established clinical technique. Several retrospective reviews have suggested that serious complications such as gangrene of the extremities have been rare, although there is a definite morbidity, in particular the occurance of thrombosis and occlusion. In order to study the safety and the frequency of complication following percutaneous radial artery cannulation for monitoring purposes, we evaluated the 300 surgical patients. Patients were examined and radial artery flow was determined by the Doppler technique 1 day to 3 days after decannulation. The results obtained were summarized as followed: 1) The incidence of arterial occiusion after cannulation was 22%, but there were no serious ischemic complications. 2) The age of the patients, the size of cannula, the frequency of the puncture and the duration of cannulation were significant factors in the occurance of the arterial occlusion. 3) Recannulation did not affect the incidence of arterial occlusion or an ischemic complication. 4) Percutaneous radial artery cannulation is a low-risk, high-benefit method of patients monitoring that deserves wide clinical use.