Abstract: AIM To assess the clinical features and relative factors of pericardial effusion in polymyositis. METHODSOne hundred and six patients with polymyositis from our cardiovascular disease research institute were included in this study. Routine information, clinical features and laboratory parameters of these patients were analyzed. Echocardiography was used to evaluate pericardial effusion. Binary logistic regression was used to assess the risk factors of pericardial effusion in polymyositis. RESULTSEighteen patients (17.0%) of the 106 polymyositis patients had pericardial effusion. Frequency of small, moderate, and large amounts of pericardial effusion in polymyositis was 67%, 28% and 6%, respectively. Logistic regression model demonstrated that heart rate (OR=1.050, 95%CI 1.001-1.102), interstitial lung disease (OR=5.274, 95%CI 1.507-18.460) and main pulmonary artery diameter (OR=1.270, 95%CI 1.015-1.589) were associated with pericardial effusion in polymyositis. CONCLUSIONPericardial effusion may be common in polymyositis, usually presenting with small or moderate amounts of pericardial effusion. Pericardial effusion is often associated with heart rate, interstitial lung disease and main pulmonary artery diameter in polymyositis.