This is the first study conducted in Grenada, with a population of approximately 108,000, to quantify the magnitude, distribution, and burden of self-reported acute gastroenteritis (AGE). A retrospective population survey was conducted in October 2008 and April 2009 and a laboratory survey from October 2008 to September 2009. The estimated monthly prevalence of AGE was 10.7% (95% CI 9.0-12.6; 1.4 episodes/ person-year), with a median of 3 days of illness. Of those who reported AGE, 31% sought medical care (stool samples were requested from 12.5%); 10% took antibiotics; 45% took non-prescribed medication; and 81% reported restricted activity. Prevalence of AGE was significantly higher among children aged <5 years (23.5%, p < 0.001). Of the AGE stool samples submitted to the laboratory for analysis, 12.1% were positive for a foodborne pathogen. Salmonella enteritidis was the most common foodborne pathogen associated with AGE-related illness. The estimated percentage of underreporting of syndromic AGE to the Ministry of Health was 69%. In addition, for every laboratory-confirmed foodborne/AGE pathogen, it was estimated that there were 316 additional cases occurring in the population. The minimum estimated cost associated with treatment for AGE was US$ 703,950 each year, showing that AGE has a potentially significant economic impact in Grenada.