We determined the prevalence and indicators of infection in intensive care unit (ICU) patients with diabetic ketoacidosis (DKA) by performing a retrospective analysis of 123 episodes of DKA (in 113 patients) managed in a medical ICU between 1990 and 1997. In univariate analysis, features associated with infection were female sex, neurological symptoms at admission, fever during the week before admission, a need for colloids, a high blood lactate level at admission, and lack of complete clearance of ketonuria within 12 h. Multivariate analysis identified 3 independent predictors of infection: female sex (odds ratio [OR], 2.31; confidence interval [CI], 1.05-5.35), neurological symptoms at admission (OR, 2.83; CI, 1.18-6.8), and lack of complete clearance of ketonuria within 12 h (OR, 3.73; CI, 1.58-9.09). Infection is the leading trigger of DKA in ICU patients. Neurological symptoms at admission and lack of complete clearance of ketonuria within 12 h are useful warning signals of infection.