The clinical course of early-onset, dominantly inherited, familial Alzheimer's disease (FAD) was contrasted with late-onset, sporadic Alzheimer's disease (AD). Eight FAD and 23 sporadic AD patients were followed over a mean of 63 months from estimated disease onset. The two groups did not differ notably in duration of symptoms from onset, global disease severity, or degree of cognitive deficits on initial evaluation. The Kaplan-Meier lifetable method was used to assess time from estimated disease onset to dependence in self-care, institutionalization, and death. A greater percentage of FAD patients became dependent in self-care and died earlier than did sporadic AD patients. The lifetable results suggest that FAD may have a more rapid course than dose late-onset sporadic AD.