Purpose : This study attempted to investigate the frequency, duration, and risk factors of antibiotic-associated diarrhea (AAD) in infants hospitalized due to febrile urinary tract infection (UTI). This is a basic research on the probiotics used in the prevention and treatment of AAD in infants. Methods : Medical records of the infants aged 3-6 months hospitalized in Gachon University Gil Hospital from January 2008 to September 2010 due to the febrile UTI were retrospectively reviewed. The episodes of loose or watery stool were investigated for frequency, onset, and duration. Those who had AAD and those who did not (non-AAD) were compared. The antibiotic regimens and the episodes of diarrhea were investigated in AAD group. Result : Total 147 infants were included. Fifty-four (36.7%) showed AAD. Intravenous third-generation cephalosporin ($3^{rd}$ CS) single therapy was used for 102 patients (69.4%), the $3^{rd}$ CS and non-$3^{rd}$ CS combination therapy for 24 (16.3%), and non-$3^{rd}$ CS combination therapy for 21 (14.3%). There was no significant difference in the dose of cefotaxime between AAD and non-AAD group (P=0.601). According to the antibiotic therapies above, in AAD group, there was no significant difference in the onset and duration of diarrhea respectively (P=0.717, P=0.830). Although the frequency of diarrhea was higher for the $3^{rd}$ CS and non-$3^{rd}$ CS combination therapy subgroup with $9.25{pm}5.30$ times/day than the other two subgroups ($7.58{pm}2.97$ times/day in $3^{rd}$ CS single therapy subgroup, $6.75{pm}4.40$ times/day in non-$3^{rd}$ CS combination therapy subgroup), there was no statistical significance (P=0.078). Conclusion : AAD seems common to the infants aged 3-6 months with febrile UTI, regardless of regimen and amount of antibiotics in usual dosage. Further research on the effects of probiotics used in the prevention and treatment of AAD in infants is warranted.