In a population-based study of 198 patients with probable early-onset Alzheimer's disease (AD), we studied the occurrence of extrapyramidal signs (tremors and rigidity), myoclonus, psychosis and seizures, as well as their predictive value for mortality. The presence of tremors was significantly associated with the presence of rigidity. The occurrence of myoclonus was significantly associated with the occurrence of seizures. Psychosis and seizures in AD patients were not associated with mortality. The occurrence of extrapyramidal signs and myoclonus at any point in time during the course of AD increased the risk of mortality significantly. When evaluating their relative importance, extrapyramidal signs appeared to be the most important predictor of mortality.