Although most cases of acute gastroenteritis require minimal medical intervention, severe dehydration and hypoglycemia may develop in cases of prolonged vomiting and diarrhea. The mainstay of treatment for mild-to-moderately dehydrated patients with acute gastroenteritis should be oral rehydration solution. Antiemetics allow for improved tolerance of oral rehydration solution, and, when used appropriately, can decrease the need for intravenous fluids and hospitalization. This issue reviews the common etiologies of acute gastroenteritis, discusses more-severe conditions that should be considered in the differential diagnosis, and provides evidence-based recommendations for management of acute gastroenteritis in patients with mild-to-moderate dehydration, severe dehydration, and hypoglycemia.