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To systematically review the literature regarding the epidemiology of functional constipation and functional nonretentive fecal incontinence (FNRFI) in children. Secondary objectives were to assess the geographical, age, and sex distribution of functional constipation and FNRFI and to evaluate associated factors.The Cochrane Library, PubMed, and Embase databases were searched from 2006 until September 2017. The following inclusion criteria were applied: (1) prospective studies of population-based samples; (2) reporting on the prevalence of functional constipation or FNRFI according to the Rome III/IV criteria; (3) in children aged 0-18 years; and (4) published in full manuscript form. A quality assessment of included studies was conducted. Random effect meta-analyses with meta-regression analyses of study characteristics were performed.Thirty-seven studies were included, of which 35 reported on the prevalence of functional constipation and 15 of FNRFI. The reported prevalence of functional constipation ranged from 0.5% to 32.2%, with a pooled prevalence of 9.5% (95% CI 7.5-12.1). The prevalence of FRNFI ranged from 0.0% to 1.8%, with a pooled prevalence of 0.4% (95% CI 0.2-0.7). The prevalence of functional constipation was 8.6% in boys compared with 8.9% in girls (OR 0.99, 95% CI 0.9-1.4). Geographical location, dietary habits, and exposure to stressful life events were reported to be associated with the prevalence of functional constipation. Data on FNRFI were scarce and no associated factors were identified.Functional constipation is common in childhood and is associated with geographical location, lifestyle factors, and stressful life events. FNRFI is rare, and no associated factors were identified.