Patients will be hospitalized for full 5 days, and asked to return for a follow up evaluation 7 days after discharge. After initial rehydration, patients will be observed for 4 hours, and only those with ³ 20 ml/kg of watery stools during this period will be enrolled for study. Treatment will be random, and blinded to study staff and patients. Clinical success of therapy will be defined as resolution of watery stool within 48 hours of administration of the study drug, and bacteriologic success will be defined as the inability to isolate V. cholerae O1 or O139 from fecal/rectal swab cultures of patients after 48 hours of therapy, i.e. on day 3 and on all subsequent days of the study. Patients in whom therapy clinically fails will be treated for 3 days with an effective alternate drug without opening the study code. Ninety one evaluable patients will be required in each group to show with a power of 80% and a type I error of 5% that the two treatment regimens are equivalent (i.e. the 95% confidence interval for the difference in efficacy between the two groups is not greater than 10%).