['We evaluate the frequency of empiric acyclovir administration to patients in the emergency department (ED) who are ultimately diagnosed with encephalitis.', "We conducted an explicit retrospective medical record review of consecutive patients discharged with a final diagnosis of herpes simplex encephalitis or viral encephalitis not otherwise specified for the period 1993 to 2003. The frequency of ED administration of empiric acyclovir was measured for patients who met the inclusion criteria of fever, neuropsychiatric abnormality, and cerebrospinal fluid pleocytosis with a negative Gram's stain result in the ED.", "Of the 90 patients reviewed, 24 (27%) met the inclusion criteria of fever, neuropsychiatric abnormality, and cerebrospinal fluid pleocytosis with a negative Gram's stain result in the ED. Of these 24 patients, 7 (29%) received empiric acyclovir in the ED, 6 (86%) patients after cerebrospinal fluid results were available, with a median time to administration of 1.5 hours (95% confidence interval [CI] 0 to 3.1 hours). The remaining 17 (71%) patients did not receive acyclovir in the ED, with median times of 16 hours (95% CI 7.5 to 44 hours) before initiation of acyclovir in inpatient settings."] Is empiric acyclovir infrequently initiated in the emergency department to patients ultimately diagnosed with encephalitis?