The invention relates to procedure and methods of determining a susceptibility to cardiac arrhythmia, including Atrial Fibrillation, Atrial Flutter and Stroke, by assessing the presence or absence of alleles at polymorphic markers found to be associated with Atrial Fibrillation, Atrial Flutter and Stroke. The invention further relates to kits encompassing reagents for assessing such markers, and diagnostic methods, uses and procedures for utilizing such susceptibility markers.