Additional reports on oral rehydration therapy (ORT) in the management of moderately dehydrated patients may convince practitioners to convert from high-cost intravenous treatment to low-cost and efficient ORT in moderately dehydrated patients. Therefore, the failure rate and its association with admission serum sodium, potassium and bicarbonate levels of 162 moderately dehydrated children with diarrhea treated with ORT were analyzed retrospectively. The overall failure rate was found to be 17.6 percent. This rate did not differ significantly among normonatremic, hyponatremic and hypernatremic patients (16%, 25% and 28%, respectively; p > 0.05), nor did the rate differ among normokalemic, hypokalemic and hyperkalemic patients (16%, 33% and 25%, respectively; p > 0.05). Only moderately and severely acidotic patients had higher failure rates than non-acidotic and mildly acidotic cases (21%, 38%, 4% and 14% respectively; p < 0.05). Severely acidotic patients were also rehydrated over a longer time (10.4 +/- 6.6 hours) than were nonacidotic patients (6.7 +/- 2.3 hours, p < 0.001). Thus the degree of acidosis, which is closely related to the clinical severity of dehydration, was found to be much more predictive of ORT failure and the duration of rehydration than were other electrolyte disturbances. Besides correcting dehydration, ORT was safe and effective in treating various electrolyte disturbances.