A retrospective analysis of 354 patients < or = 2 years of age with urinary tract infections (UTIs) was performed to characterize patients with bacteremia or meningitis and to identify any objective predictors of these complications. Thirty-three patients with bacteremia were identified. Blood culture isolates included Escherichia coli (25), Staphylococcus aureus (4), enterococcus (1), group B Streptococcus (2), and Enterobacter (1). Besides one patient with group B Streptococcus bacteremia at 1.5 months of age, all bacteremias after one month of age were with E. coli. Bacteremia was limited to those < 6 months old and inversely related to age (R = 0.24, P = 0.0008). Grouped by age, the incidence of bacteremia was 21% for 0 < or = 1 month, 13% for 1.1-2.0 months, 4% for 2.1-3.0 months, and 8% for 3.1-6.0 months. Mean white blood cell count, initial temperature, initial serum bicarbonate, and erythrocyte sedimentation rate were not statistically significant between bacteremic (B) and nonbacteremic (NB) patients. Statistically significant differences were noted for percentage of bands (6.2% [NB] vs. 12.3% [B] P < 0.001), total band count (1048 [NB] vs. 2252 [B] P < 0.001), and band-neutrophil ratio (0.16 [NB] vs. 0.36 [B] P = 0.01); however, no practical value for any of these measures would reliably discriminate between bacteremic and nonbacteremic patients. Four patients, all neonates, had meningitis; too few patients with meningitis were identified for analysis. In summary, bacteremia with UTIs was observed to be inversely related to age and limited to patients less than six months of age. No objective parameters were identified to distinguish patients with bacteremia at the time of presentation.