Valaciclovir is metabolized to acyclovir after ingestion and thereafter exerts its antiviral activity. Because of its superior pharmacokinetic profile, it has quickly replaced acyclovir in the treatment of herpesvirus infection. Neurotoxicity caused by valaciclovir has been reported, however, among patients with pre-existing impaired renal function. This paper reports a case of neurotoxicity of valaciclovir in a patient with end-stage renal disease who was undergoing continuous ambulatory peritoneal dialysis (CAPD). A 67-year-old female on CAPD took 500 mg of valaciclovir twice for herpes zoster. After she took her second dose orally, she developed confusion and disorientation, along with involuntary movements. Her mental confusion progressed to a coma. Discontinuation of valaciclovir showed no rapid improvement. There- fore, hemodialysis was started. After two sessions of hemodialysis, the patient became alert; and after four sessions of hemodialysis, her neurological abnormalities were completely reversed. In conclusion, valaciclovir can induce life-threatening neurotoxicity, especially in CAPD patients, even with appropriate dose reduction, which can be effectively managed by hemodialysis.