The magnetic resonance imaging (MRI) findings in eight patients with herpes simplex meningoencephalitis were reviewed: 14 examinations were analysed. The most striking finding was high signal intensity in the temporal lobe(s) with the typical configuration known from CT. Meningeal enhancement after Gd-DTPA administration was clearly seen in four patients. Haemorrhagic changes are much better seen on MRI than on CT. When adequate motion control can be achieved, MRI becomes the examination of choice in the diagnosis and follow-up of herpes simplex encephalitis. Localized 1H MR spectroscopy also proved promising in the study of neuronal loss.