The purpose of this retrospective cohort study was to determine the rate and prediction of infection in children, < or = 21 years, with diabetic ketoacidosis (DKA). Over a 6-year period, 247 admissions were identified. There were 171 (69%) with no infection, 44 (17.8%) with presumed viral infection, and 32 (12.9%) with bacterial infection. The mean WBC for all patients was 17,519 ( +/- 9,582). 118 (50%) had leukocytosis as defined by a WBC > or = 15,000/mm3. WBC, differential, leukocytosis, as well as sex, temperature and new onset diabetes, were not significant predictors (P > .05) of bacterial infection. Bacterial infections were more common in children < or = 3 years of age (P = .03). There was a significant correlation of WBC with both pH (r = -0.59, P < .001) and bicarbonate (r = -0.43, P < .001). In conclusion, most children in DKA have no evidence of infection. Leukocytosis is common but most likely reflects the severity of DKA rather than the presence of infection.