The authors compared the safety and efficacy of a ready-to-use, premixed, rice-based oral rehydration solution (R-ORS) with a glucose-based oral rehydration solution (G-ORS), each containing 75 mmol/L sodium, in Mexican children with acute diarrhea for less than 5 days. METHODS One hundred eighty-nine boys 3 to 24 months old admitted to the hospital with acute diarrhea and signs of dehydration were randomly assigned to receive either G-ORS or R-ORS. Intake and output were measured every 3 hours. RESULTS In the group treated with R-ORS, significantly fewer patients required supplemental intravenous fluids during the rehydration phase compared to the G-ORS group (1% v 8.7%; P < 0.01). Mean stool output, percent weight gain, ORS intake, urine output, and number of patients who vomited during rehydration were similar in the two groups. The mean total stool output after the first 24 hours of maintenance phase was significantly lower in the R-ORS group than in the G-ORS group. CONCLUSIONS The authors found rice-based ORS to be safe, and its use reduced the rate of intravenous fluid therapy in comparison with the use of a glucose-based ORS.