This article continues the series on cardiac monitoring in the peri-operative area by reviewing those arrhythmias that are classified as atrial or supraventricular. Whilst these arrhythmias are rarely life threatening, their haemodynamic effects can be significant and may not be tolerated in conjunction with the concurrent operative procedures. These arrhythmias are however, very commonly seen in perioperative practice and may be associated with anaesthetic procedures, surgical techniques and the recovery phase. In this increasingly technological age, it is imperative that perioperative practitioners can recognise and respond appropriately to the rhythms observed on the cardiac monitor.