Objeetlve To avoid inserting the tip of the central venous catheter into internal jugular vein (IJV) through subclavian vein under ultrasound guidance.Methods sixty breast cancel patients aged 28-63 yr weighing 41-70 kg who needed long-term intravenous infusion and chemotherapy through central venous catheter were randomly divided into 2 groups (n=30 each):control group (group C) and ultrasound group (group U).In group C the insertion of central venous catheter through subclavian vein was guided by pulsatile injection of ice-cold saline.In group U ultrasound detector (type HFL 38/13-6 MH,Sonosite Co,USA) was used to guide the insertion of tbe central vesons catheter.The position of the catheter tip was verified by X-ray radiography.The rate of successful placement at 1st attempt was calculated.Results The tip of the central venous catheter was correctly placed in the vena cava and right atrium in all patients in group U (success rate 100%),while in group C the tip was misplaced in IJV in 6 patients (success rate 80%) and had to be replaced.Conclusion Ultrasound guidance is effective for correct placement of the tip of central venous catheter in the vema cava and right atrium through subclavian vein.