PURPOSE: To assess the usefulness of the ultrasound-guided subclavian vein catheterization in difficult patients. MATERIALS AND METHODS: We tried subclavian vein catheterization in 18 patients in which conventional blind technique failed(N=9) :or was complicated by hemothorax or pneumothorax(N=3) :or was prohibited by respirator care(N=4) and severe thoracic deformity(N=2). Initially, the patency of subclavian vein was evaluated with ultrasonography, and then, the puncture of the subclavian vein was performed under the guidance of ultrasonography. Under the fluoroscopy, the patency of the proximal subclavian vein and the superior vena cava was evaluated after contrast-media injection and a catheter was inserted into the subclavian vein and accurately positioned at the superior vena cava. RESULTS: Successful catheterization was performed in 17 patients. In the remaining one patient, we did not perform catheterization because of bilateral subclavian vein thrombosis detected during the procedure. There were no procedure-related complications. CONCLUSION: Ultrasound-guided subclavian vein catheterization is an easy and safe method even in difficult cases.