Bacteremia in children under 2 years of age is not uncommon. Several studies indicated that a small proportion of young children with fever who do not appear to be seriously ill may have bacteremia, and a small proportion of this subgroup may go on to develop serious illness such as meningitis. The rationale for this study was to assess both the incidence of bacteremia in febrile children in Taipei area and the predictive value of the white blood cell count and degree of body temperature for bacteremia. Three hundred febrile children (B. T. greater than or equal to 39 degrees C), without underlying disease or readily recognizable viral illness, who visited the emergency service of Chang Gung Memorial Hospital, were enrolled. Blood cultures and complete blood counts were obtained. Clinically important pathogens were identified in 6 of 300 cases (2%). The incidence and pathogens of various age group were: (1) Neonate, 2/15 (13%), one each of Group D streptococcus & streptococcus viridans; (2) 1 month to 1 year old, 3/66 (5%), 2 Escherichia coli and 1 Salmonella Group D; (3) 1 to 2 years old, 0/49; (4) 2 to 5 years old, 0/72; (5) 5 to 10 years old, 0/67; (6) 10 to 15 years old, 1/26 (4%), Salmonella typhosa. Neither the white blood cell count, the absolute segmented or band neutrophil count, nor the degree of body temperature had predictive value for bacteremia.