Twenty-two infants with moderate dehydration due to diarrhea in whom oral rehydration therapy (ORT) was contraindicated or who failed to respond to this method of therapy were treated with rapid intravenous rehydration (RIR). Clinical signs of dehydration without shock allowed us to estimate 5% to 10% of weight loss. Patients were 11 days to 19 months old, and 9 of them were undernourished. A standard solution containing 90 mmol/L sodium, 80 mmol/L chloride, 30 mmol/L bicarbonate, 20 mmol/L potassium and 111 mmol/L glucose was used for all patients. The IV infusion was maintained until the rehydration was completed at a rate of 15 to 20 mL/kg/hour. Complete rehydration was successfully achieved in all patients. A total of 89.5 +/- 25.0 mL/kg (mean +/- SD) was needed and the duration of the IV infusion was 5.1 +/- 1.6 hours. Weight gain achieved was 6.5 +/- 1.6%. None of the patients developed hypernatremia following treatment. The initial base deficit, -9.5 +/- 6.6, was reduced to -3.5 +/- 2.9. All of the patients tolerated refeeding immediately after completion of the IV infusion. Our study suggests that this modality of rehydration is well tolerated, safe and effective and enhances the possibility of an early hospital discharge.