To define risk factors for mortality due to bacteremia and fungemia of childhood, 242 episodes (for which the mortality rate was 19%) were studied prospectively by univariate and multivariate analyses. The mortality rate was higher in neonates (23%) and in individuals 10-18 years old (26%) than in infants and young children (10%-16%). The mortality rate was 29% for children who had neutropenia, 29% for those who had received therapy with steroids, 26% for those who had received antibiotics, and 75% for those who were in septic shock. The fatality rates for polymicrobial bacteremia (40%), recurrent bacteremia (67%), and hospital-acquired bacteremia (28%) were higher than those for other types of bacteremia; the fatality rate was related to inappropriate empiric antibiotic treatment or to the specific organism isolated (mortality rates associated with the latter ranged from 0 to 60%). Seven variables that independently and significantly affected mortality were defined with use of multivariate logistic regression analysis: septic shock (odds ratio [OR], 26.4); polymicrobial (OR, 5.4), recurrent (OR, 4.5), or hospital-acquired (OR, 4.3) bacteremia; candidemia (OR, 3.6); inappropriate antibiotic treatment (OR, 2.4); and neutropenia (OR, 2.3). These variables should be considered for adequate management of bacteremic patients who are at high risk for death.