BACKGROUND Several cases of herpes simplex virus type 1 meningoencephalitis (HSVE) have been reported in patients receiving steroids, but the exact contribution of steroids to the disorder remains unclear because other risk factors, such as chemotherapy, brain radiation, or surgery, were present in almost all cases. CASE REPORT We report the case of a 76-year-old man who developed HSVE following the administration of pulse-dose steroids. The patient had occupational asbestos exposure and a chronic interstitial lung disease of unclear etiology (sarcoidosis versus hypersensitivity pneumonitis) and was admitted for acute-on-chronic respiratory failure requiring mechanical ventilation. After a negative infectious workup and several days of antibiotics without improvement, pulse-dose steroids were administered. In the following days, the patient developed a fever and worsening encephalopathy. A lumbar puncture showed elevated nucleated cells and positive polymerase chain reaction for herpes simplex virus 1 in the cerebrospinal fluid, confirming the diagnosis of HSVE. Acyclovir treatment was initiated, but the patient later died as a result of persistent severe encephalopathy and respiratory failure with an inability to wean mechanical ventilation. CONCLUSIONS Clinicians should keep in mind that HSVE is a potential complication of steroids and carefully consider the benefit/risk ratio of pulse-dose steroids, taking into account associated factors of immunosuppression. A high level of awareness should be especially maintained in critically ill patients because of associated risk factors (critical illness immune paralysis) and because neurological signs of HSVE may be missed in mechanically ventilated, sedated patients.