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The prognostic relevance and the prevalence of pericardial effusion in several diseases are not well established. The aim of this meta-analysis is to summarize the available evidence related to pericardial effusion prevalence and outcomes according to the cause.Articles investigating the prognosis of pericardial effusion were identified by literature search. Twenty-three studies were finally included (17 022 patients). All-cause mortality was the primary end-point. Secondary end-point was the prevalence of pericardial effusion in most common diseases related to this clinical condition.The pooled prevalence of pericardial effusion was 19.5% [95% confidence interval (CI): 14.3–26]. After a mean follow-up of 36 ± 23 months, the risk of death was higher in pericardial effusion patients [hazard ratio (HR) 1.59, 95% CI 1.37–1.85, P < 0.0001]. Stratifying for the main disease, pericardial effusion is associated with unfavourable outcome in all available subgroups: pulmonary arterial hypertension HR 1.53 (95% CI: 1.22–1.92; P < 0.0001), chronic heart failure (CHF) HR 1.53 (95% CI: 1.22–1.92; P < 0.0001), myocardial infarction HR 2.65 (95% CI: 1.4–4.99; P = 0.003) and malignancies HR 1.75 (95% CI: 1.09–2.81, P = 0.021). The lack of data concerning the idiopathic pericardial effusion does not permit a secure risk assessment but the average incidence of mortality is 14.5% (95% CI: 7.7–25.6).Pericardial effusion should be considered a marker of the severity of the underlying disease, whereas for idiopathic pericardial effusion the correlation with poor prognosis is less clear.