We evaluated 160 electrocardiograms taken after placement of central venous catheters (CVC) to determine their locations. Usable recordings were obtained in 154 patients. Subsequent radiographs revealed 30 misplaced catheters. Twenty-five of those were detected by CVC electrocardiograms. There were five false positive and five false negative traces. The sensitivity of CVC electrocardiography was 96%, the specificity 83.3%, and the total predictive power 93.5%. Electrocardiograms obtained from guide-wires were of significantly better quality than those from 0.9% NaCl filled catheters. The technique is accurate, safe and easy to learn. It may reduce the need for routine radiographic control to less than 10% of patients.