Long-term survival was examined for 218 patients with Alzheimer's disease (AD) and 115 patients with multi-infarct dementia (MID). The 14-year survival rate for AD was 2.4% versus an expected rate of 16.6%, and for MID 1.7% versus 13.3% expected. MID showed a more malignant natural course than AD. Men carried a less favourable survival prognosis than women, both in AD and MID: the relative risk of dying for women was half that for men in both diseases. In MID, advanced disability indicated a relative risk of dying over twice as high. In both diseases the risk of death was substantially higher in the event of occurrence of primitive reflexes.