A 35-year-old patient with terminal renal failure who had received 30 mg piperazine hexahydrate/kg body weight daily for 10 days for oxyuriasis was subsequently admitted to hospital in precoma with severe clinical symptoms not unlike those observed in so-called dialysis dementia: loss of consciousness, dysarthria, apraxia, clonic spasms, tremor, muscular weakness, dropping of objects, inability to think clearly and/or hallucinations. The EEG showed disturbances with diffuse, multifocal delta waves. Under maintenance hemodialysis the patient became asymptomatic one week after discontinuation of the piperazine therapy. Piperazine is contraindicated in patients with renal failure.