Atrial fibrillation (AF) is a common tachyarrhythmia. There are over 2 million patients in the US with AF currently1, and as the median age of the population increases, the prevalence of AF likely will as well. Strategies for treating AF are diverse, and include options ranging from simple observation to pharmacotherapy to catheter-based and surgical interventions. Therapeutic approaches to AF historically have been divided into rate-control and rhythm-control categories, the former focusing on simply reducing ventricular response rates and the latter on restoration of sinus rhythm. Over the last 15 years, there has been an explosion of rhythm-control therapies, particularly in the field of catheter-based ablation. The proliferation of these ablative approaches has led to new insights into AF, both in terms of the mechanism(s) of the disease itself, and in the potential harm that patients can suffer during attempts at restoration of sinus rhythm. This review focuses on the complications, both the familiar and the newly appreciated, that may occur during catheter ablation of AF.