In an attempt to improve the accuracy of central venous pressure (CVP) catheter tip location, 84 consecutive cardiac surgery patients in sinus rhythm were studied prospectively with respect to subclavian insertion of a CVP catheter using a guidewire technique. The presence of cardiac arrhythmia was used as an index of right atrial (RA) location of the guidewire tip, before threading the catheter over the guidewire. Correct catheter tip location (superior vena cava [SVC] or RA) was achieved in 100% of patients (N = 78) with premature atrial contractions (PACs) related to guidewire insertion. This fell to 50% (N = 4) if no arrhythmias were noted from the guidewire. Ventricular arrhythmias were noted in two of 84 patients (2.4%). Other problems related to the use of this technique are discussed.