OBJECTIVE To compare the efficacy of two commonly used solutions in the rehydration of infants with mild to moderate dehydration caused by acute diarrhea in the United States. METHODS Double-blind, parallel-group, randomized study performed at Children's Hospital Medical Center. METHODS Sixty infant boys (< or = 2 years old), with mild (< or = 5%) or moderate (6 to 9%) dehydration caused by acute diarrhea of less than 1 week's duration were included in the study. METHODS Infants were randomly assigned to receive treatment with either a glucose-based oral rehydration solution (ORS) (Pedialyte, Ross Laboratories, Columbus, OH) or a rice syrup solids-based ORS (Infalyte, Mead Johnson Nutritional Group, Evansville, IN). After rehydration was achieved, patients entered a maintenance phase during which, in addition to a maintenance ORS, breast milk or a soy-based formula was offered; infants older than 1 year were also given a lactose-free diet. METHODS Rehydration was judged clinically. Infants remained on a metabolic bed during the study in to separate and quantitate urine and stool output. Therefore, in addition to clinical outcome, we compared intake, output and apparent absorption and retention of fluid, sodium, and potassium between groups. RESULTS All patients were successfully rehydrated using an ORS without the use of intravenous fluids. No differences were detected between treatment groups in time to rehydration, percentage of weight gain after rehydration, consumption of ORS to achieve rehydration, or stool output. However, the apparent sodium absorption (net intake less fecal output) was greater in the Infalyte group than the Pedialyte group during the first 24 hours. CONCLUSIONS The two maintenance oral electrolyte solutions (Pedialyte and Infalyte) most commonly used in the United States are effective as rehydration solutions for infants with mild to moderate dehydration. We speculate that a strategy for oral rehydration therapy in the United States, based on the use of a single solution during the rehydration and maintenance phase, might gain additional acceptance by practicing pediatricians and family physicians.