Visual hallucinations are commonly associated with seizures, drug effects, psychiatric disorders, or visual loss as 'release' phenomena. We report the case of a previously healthy 65-year-old woman, who was admitted to hospital with intermittent headache episodes accompanied by complex visual hallucinations. During these episodes the patient's blood pressure was 220/120 mmHg. In between symptomatic episodes she had no complaints and felt healthy. The neurological and ophthalmological examinations were normal but cerebral magnetic resonance imaging (MRI) showed multiple white matter abnormalities in the parieto-occipital regions. Rapid reversal of the symptoms and imaging abnormalities occurred concurrently with lowering of blood pressure. The history and the findings were similar to those recently described in the clinicoradiological 'posterior leukoencephalopathy' syndrome. Different pathogenic mechanisms are discussed. Copyright 1998 Lippincott Williams & Wilkins