Central venous catheters used for chemotherapy are usually sited so that the catheter tip lies in the superior vena cava. This study evaluated right atrial electrocardiography as a method of accurately placing the catheter tip in 34 patients over a period of 22 months. An electrocardiograph adaptor was connected to the catheter and the tip advanced into a central vein until a biphasic P wave was identified. In 31 of 34 patients the characteristic P wave changes were observed and the position of the catheter tip confirmed by screening to be in the superior vena cava. Right atrial electrocardiography is an accurate, reliable and rapid method of positioning the tip of a central venous catheter, and avoids or reduces exposure to radiation.