A 45-year-old man presented with severe hypertension, headache, cortical blindness, and a depressed level of consciousness. A second patient, a 33-year-old woman, was admitted with pre-eclampsia. She developed lethargy, headache, bilateral extensor plantar responses, and seizures. The third patient, a 62-year-old man, presented with acute renal failure due to necrotising vasculitis and glomerulonephritis. Five days after treatment with immunosuppressive drugs had been initiated, he developed headache, confusion, seizures, and cortical blindness. Hypertensive encephalopathy is characterised by headache, vomiting, disturbances in cognition and level of consciousness, visual abnormalities, and seizures. Imaging studies often demonstrate oedema of the white matter in the posterior parietal and occipital areas of the brain. This so-called reversible posterior leucoencephalopathy syndrome is well known in patients with severe hypertension, but it is also associated with immunosuppressive drug use and renal failure. It can be recognised by its fairly characteristic clinical features (different combinations of headache, vomiting, changes in cognition and level of consciousness, seizures, muscle weakness, and visual symptoms) and by its specific imaging findings. Treatment consists of reducing the blood pressure and reducing or discontinuing the use of immunosuppressive drugs. If the treatment is started promptly, symptoms and imaging abnormalities are usually reversible.