Atrial fibrillation (AF) is the commonest sustained arrhythmia in clinical practice, but its treatment is still a challenge for modern cardiology. During the last decade new insights regarding AF genetic background have been achieved. Familial aggregation suggesting a potential heritability was well known in the pre-molecular era. Now, research on the molecular basis of the disease is providing evidence that familial AF is mostly autosomal, both dominant and recessive, and genetically heterogeneous. Mutations in several disease genes with different functional effects may be associated with AF. Early results encourage family studies and monitoring. In addition, genome-wide association studies have recently identified common polymorphisms associated with an increased risk of AF in different large populations. These studies are contributing to provide early answers, but also raise new questions. In this review we analyze existing knowledge on genetics of AF and related potential clinical impact.