A 12-lead ECG is a routine non-invasive investigation regularly performed by healthcare professionals on adults in both hospital and community settings. The patient’s chest is exposed during this procedure, so after an explanation is given, consent gained and equipment prepared, privacy and dignity must be maintained. A supine position is preferred. To ensure good electrode contact, skin may need to be washed and dried or excess hair removed by shaving. Ensure the patient is relaxed whilst the recording is taken; the name of the patient, hospital number, date and time is recorded on the ECG printout. The ECG then requires interpretation by a competent member of the healthcare team. Cardiac arrhythmias, evidence of heart failure, myocardial ischaemia or infarction may be diagnosed with the aid of the 12-lead ECG. Chapter 30 discusses lead placement and ECG interpretation in more detail.