OBJECTIVE: The FEBSTAT study is a prospective study that seeks to determine the acute and long-term consequences of febrile status epilepticus (FSE) in childhood. METHODS: From 2003 to 2010, 199 children age 1 month to 5 years presenting with FSE (>30 minutes) were enrolled in FEBSTAT within 72 hours of the FSE episode. Of these, 191 had imaging with emphasis on the hippocampus. All MRIs were reviewed by 2 neuroradiologists blinded to clinical details. A group of 96 children with first simple FS who were imaged using a similar protocol served as controls. RESULTS: A total of 22 (11.5%) children had definitely abnormal (n = 17) or equivocal (n = 5) increased T2 signal in the hippocampus following FSE compared with none in the control group (p < 0.0001). Developmental abnormalities of the hippocampus were more common in the FSE group (n = 20, 10.5%) than in controls (n = 2, 2.1%) (p = 0.0097) with hippocampal malrotation being the most common (15 cases and 2 controls). Extrahippocampal imaging abnormalities were present in 15.7% of the FSE group and 15.6% of the controls. However, extrahippocampal imaging abnormalities of the temporal lobe were more common in the FSE group (7.9%) than in controls (1.0%) (p = 0.015). CONCLUSIONS: This prospective study demonstrates that children with FSE are at risk for acute hippocampal injury and that a substantial number also have abnormalities in hippocampal development. Follow-up studies are in progress to determine the long-term outcomes in these children.