The Global Enteric Multicenter Study (GEMS-1) was a multi-country case-control study of diarrheal disease in children under five years of age. Study sites in each country were required to have access to some type of demographic surveillance system for tracking participants and at least one healthcare facility that provided care to children of that population with diarrhea. A Health Utilization and Attitudes Survey (HUAS) of 1,100 households in the selected population was conducted in each country prior to starting the case-control portion of the study, in which 660 children with mild-to-severe diarrhea (cases) and a matching 660 of children without diarrhea (controls) were enrolled in the study in each of 3 age strata (0-11, 12-23, and 24-59 months). Participants were examined at initial enrollment and again after approximately 60 days; anthropometric measurements were collected at both the enrollment exam and followup home visit, and stool samples were collected at the enrollment exam.