This is the first report of ertapenem-associated CNS toxicity in patients on regular HD and utilizing the plasma ertapenem concentration to demonstrate the causal relationship. The recommended dosage of 500 mg ertapenem daily may be still too high in regular HD patients, especially in Asians, owing to their relatively small body size. An increased awareness of ertapenem-associated CNS toxicity would avoid unnecessary examinations, hospitalization, and potentially catastrophic complications.