ABSTRACT. Objective. To assess the apparent increase in the diagnosis of Lemierre syndrome (LS) and other Fusobacterium necrophorum infections at a large children's hospital. Infections with F necrophorum ranged from peritonsillar abscess to potentially fatal LS. LS is an oropharyngeal infection characterized by septic thrombophlebitis of head and neck veins, complicated by dissemination of septic emboli to pulmonary and systemic sites.Methods. Review of the medical and laboratory records was conducted of all patients who were seen at or admitted to the Children's Hospital of Wisconsin with the diagnosis of LS and/or isolation of F necrophorum from a clinical specimen between January 1995 and January 2002.Results. During the 7-year period of the study, there was an increase in the isolation of Conclusions. The cause for the recent increase in the number of serious infections caused by F necrophorum infection diagnosed at our institution is unclear but does not seem to be related to changes in microbiologic techniques or patient demography. We speculate that it could be attributable, in part, to alterations in antibiotic usage patterns in our region. Clinicians need to be aware of the increasing clinical importance of F necrophorum infections and the life-threatening nature of LS. Pediatrics 2003;112:e380 -e385. URL: http://www.pediatrics.org/cgi/ content/full/112/5/e380; Fusobacterium necrophorum, Lemierre syndrome, peritonsillar abscess, thrombophlebitis, pulmonary emboli.