Central pontine myelinolysis (CPM) is an uncommon complication in sick patients with severe underlying disorders such as chronic alcoholism, malignancy, malnutrition and hyponatraemia. We report two patients with advanced HIV infection who developed CPM. In one case the diagnosis was not suspected in life, in the other the diagnosis was made just before death, on the basis of magnetic resonance (MR) imaging appearances. At post mortem there was a close correlation between the MR abnormalities and the anatomic changes in the pons.