This study was undertaken to investigate the suitability of rifaximin for short-term treatment of acute bacterial diarrhea in children receiving long-term prophylactic therapy for urinary tract infections. Using a 2:1 ratio, 46 children (mean age, 4.9 years) mere consecutively assigned to receive either rifaximin oral suspension (n = 30) or oral rehydration (control group, n = 16) for a maximum of 5 days. After 5 days, in the rifaximin groups, 15 patients (50.0%) mere clinically cured, 13 (43.3%) improved, and 2 (6.7%) had an insufficient outcome. In the control group, 5 patients (31.2%) were clinically cured after 4 days, 2 patients (12.5%) improved after 5 days, 4 (25.0%) had a sufficient outcome, and 5 (31.2%) had an insufficient outcome. Stools normalized rapidly during treatment,vith rifaximin-formed stools were detected in 24 children (80.0%) on treatment day 1. Only 2 patients still had watery stools after 5 days of treatment. In the control group, patients' stools normalized after 4 days in 7 children (43.8%) and after 5 days in 2 (12.5%); stools had not normalized by the end of the 5-day period in the remaining 7 patients (43.8%). Overall, a quick and statistically significant remission of fever and other clinical symptoms mas seen with rifaximin. In the control group, symptoms were reduced more slowly. No adverse events, withdrawals, or dropouts occurred in the rifaximin group. The rapidity, effectiveness, and safety of rifaximin suggest that it is suitable for the treatment of acute recurrent episodes of diarrhea in children periodically undergoing prophylactic therapy for other genitourinary pathologic conditions.