Objective: To determine the incidence and potential risk factors for developing febrile illness in infants during the first 8 weeks of life.Methods: Families of 72 infants 8 weeks or younger were interviewed during admission for a febrile illness to our pediatric ward from 8/92 - 2/95. Data was compared with a prospectively enrolled, randomly chosen cohort of 207 in-bom infants evaluated by parental telephone interview every 2 weeks during the first 8 weeks of life over the study period. Factors included general demographics, nursery course, home environment, and in-home and out-of-home contacts. Univariate analysis was by chi-square, t-test, or Mann-Whitney Rank Sum test, with logistic regression performed for variables meeting threshold significance. Results: The incidence of admission for febrile illness during the first 2 months was 1.9%, with an additional 2.8% who developed fever but were not brought to medical attention. The mean age of admission was 5 1/7 weeks with three quarters occurring after 4 weeks. Univariate analysis revealed significant differences between the admitted and control groups for matemal smoking rate (18% vs 5%, p=0.002), the presence of a 0-3 year old (58% vs 30%, p<0.0001), and the presence of a household member with a concurrent illness (68% vs 34%, p<0.0001) or a febrile illness (35% vs 10%, p<0.0001). Admitted infants were more often taken on trips to “low density” locations (which tended to be family and friends), and less likely to have been taken to “higher density” locations (which tended to be malls and shopping) (p<0.01). Gestational age was statistically different by univariate analysis, but dropped out in the logistic regression model. Factors significant by logistic regression were: 1) the presence of an ill household member, 2) increased frequency of trips to “low density” locations, 3) the presence of another 0-3 year old in the household, and 4) matemal smoking.Conclusion: Febrile illness in the first 8 weeks of life is common, but with significant parental screening before medical evaluation. Major associated risk factors were related to in-home exposures, with the exception of trips to locations such as family and friends. We speculate that physician and parental awareness of these factors may lead to decreased disease transmission in this age group (i.e. focus on handwashing, closer observation of young siblings, encouragement of mothers to stop smoking.) A preventative approach is needed to address the significant incidence and costs associated with evaluation of fever in the young infant.