Empirical treatment is indicated for young children with febrile urinary tract infection (UTI). In this clinical setting, oral antibiotics are as safe and effective as intravenous therapy. The aim of this study was to investigate in children with febrile UTI whether there were longitudinal changes in the prevalence of bacteria and in the pattern of Escherichia coli susceptibility to oral antimicrobial agents. Two hundred and eighty-seven positive urine cultures from children (1 month to 12 years) with febrile UTI collected over three periods (1986–1989, 1990–1991, and 1997) were studied. E.coli was the most-prevalent microorganism in all three study-periods (n=228). The susceptibility pattern of E.coli to nitrofurantoin (92%, 95%, 94%) and nalidixic acid (85%, 92%, 95%) did not present any statistically significant differences (P>0.05) over time. There was a significant increase (PE. coli susceptibility to cephalexin (65%, 54%, 81%). The E.coli susceptibility to trimethoprim-sulfamethoxazole (40%, 85%, 40%) behaved differently. Initially there was a significant rise (PP<0.05). Empirical oral treatment with nitrofurantoin or nalidixic acid can safely be started in children with febrile UTI seen in the Emergency Department, Hospital de Clínicas de Porto Alegre, Brazil.