AIM: To assess the functional gastrointestinal disorders(FGID) prevalence in infants and toddlers. METHODS: Pub Med, EMBASE, and Scopus were searched for original articles from inception to February 2016. The literature search was made in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA). For inclusion, each study had to report epidemiological data of FGID on children up to 4 years old and contain standardized outcome Rome Ⅱ or Ⅲ criteria. The overall quality of included epidemiological studies was evaluated in accordance to Loney’s proposal for prevalence studies of health literature. Two reviewers assessed each study for inclusion and extracted data. Discrepancies were reconciled through discussion.RESULTS: It was identified a total of 101 articles through the databases and two through the manual search. A total of 28 articles fulfilled the eligibility criteria. After reading the full articles, 13 of them were included in the present review. Twelve studies were written in English and one in Chinese, and published between 2004 and 2015. Eight articles(61.5%) were performed in Europe, three(23.1%) in America and two(15.4%) in Asia. Sample size varied between 45 and 9660 subjects. Cross-sectional frequency was reported in majority of studies(k = 9) and four studies prospectively followed the subjects. 27.1% to 38% of participants have met any of Rome’s criteria for gastrointestinal syndromes, of those 20.8% presented two or more FGID. Infant regurgitation and functional constipation were the most common FGID, ranging from less than 1% to 25.9% and less than 1% to 31%, respectively. Most included studies were of moderate to poor data quality with respect to absence of confidential interval for prevalence rate and inadequate sampling methods.CONCLUSION: The scarcity and heterogeneity of FGID data call for the necessity of well-designed epidemiological research in different levels of pediatric practice and refinement of diagnostic. METHODS: Pub Med, EMBASE, and Scopus were searched for original articles from inception to February 2016. The literature search was made in accordance with the Preferred Reporting Items for Systematic For inclusion, each study had to report epidemiological data of FGID on children up to 4 years old and contain standardized outcome Rome II or III criteria. The overall quality of included epidemiological studies was evaluated in accordance with to Loney’s proposal for prevalence studies of health literature. Two reviewers assessed each study for inclusion and extracted data. Discrepancies were reconciled through discussion .RESULTS: It was identified a total of 101 articles through the databases and two through the manual search. A total of 28 articles fulfilled the eligibility criteria. After reading the full articles, 13 of them were included in the present revie Twelve studies were written in English and one in Chinese, and published between 2004 and 2015. Eight articles (61.5%) were performed in Europe, three (23.1%) in America and two (15.4%) in Asia. Sample size varied Between 45 and 9660 subjects. Cross-sectional frequency was reported in majority of studies (k = 9) and four studies prospectively followed the subjects. 27.1% to 38% of participants have met any Rome’s criteria for gastrointestinal syndromes, of those 20.8% presented two or more FGIDs. Infant regurgitation and functional constipation were the most common FGID, ranging from less than 1% to 25.9% and less than 1% to 31%, respectively. Mostly included studies were of moderate to poor data quality with respect to absence of confidential interval for prevalence rate and inadequate sampling methods. CONCLUSION: The scarcity and heterogeneity of FGID data call for the necessity of well-designed epidemiological research in different levels of pediatric practice and refinement of diagn ostiFrom.