We carried out examination of 103 probands with atrial fibrillation (AF) and 301 their 1st, 2nd, and 3rd degree relatives (main group). In addition we examined 82 probands without clinical electrocardiographic signs of heart disease and 163 their 1st and 2nd degree relatives (control group). We found accumulation of AF in families of probands with this pathology. Segregation analysis of idiopathic forms of AF allowed to reveal autosomal dominant type of inheritance of this pathology. Heterozygous variant of Ser49Gly of betai-adrenoreceptor gene can be considered as one of genetic predictors of development of how primary and secondary AF.