心房纤颤是常见的心律失常，多见于某些器质性心脏病患者。但作者所见一家兄妹三人同患不明原因的心房纤颤，极为少见，现报告如下。例１：患者男，５０岁。因心悸５年于１９８６年７月入院，无慢性咳嗽及其他病史。查体：血压１５．６／１０．４ｋＰａ，发育正常，自动体位， Atrial fibrillation is a common arrhythmia, more common in some patients with organic heart disease. However, the author saw a sibling with unknown causes of atrial fibrillation, is extremely rare, are as follows. Example 1: Male patient, 50 years old. 5 years due to heart palpitations in July 1986 admitted, no chronic cough and other medical history. Physical examination: blood pressure 15.6 / 10.4kPa, normal development, automatic position,