Background - Infectious encephalitis is a rare but serious condition whose cause is rarely identified. Method - We conducted a prospective, multicenter descriptive study in mainland France in 2007 to determine the etiological diagnosis of infectious encephalitis. A case was defined as a hospitalized patient with signs of acute infection, abnormal cerebrospinal fluid, fever, and central neurological signs. Standardized etiological testing was performed. Results - A total of 253 cases were included, of which 131 (52%) had an identified etiology. The most common causative agents were herpes simplex virus (HSV), varicella zoster virus (VZV), Mycobacterium tuberculosis, and Listeria monocytogenes. Twenty-six patients died, and 145 continued to experience symptoms after hospitalization. Conclusion - This study highlights the importance of viruses (HSV and VZV) as well as certain bacteria in the epidemiology of infectious encephalitis. These common causes must be taken into account to improve the management and prognosis of patients with these conditions. (R.A.) Article adapted from Mailles A, Stahl JP; Steering Committee and Investigators Group. Infectious encephalitis in France in 2007: a national prospective study. Clin Infect Dis. 2009;49(12):1838-47. Adapted from Mailles A, Stahl JP; Steering Committee and Investigators Group. Infectious encephalitis in France in 2007: a national prospective study. Clin Infect Dis. 2009;49(12):1838-47. http://opac.invs.sante.fr/index.php?lvl=notice_display&id;=855