A random sample of 60 late-onset Alzheimer's disease (AD) cases from a population-based study were apolipoprotein E (apoE) genotyped and clinically examined with a 3-year interval. The epsilon 4 allele carriers had a significantly lower age of disease onset compared to non-epsilon 4 carriers. However, no significant differences were observed between epsilon 4 allele carries and non-carriers for Mini-Mental State Examination (MMSE) test scores at the first examination, in spite of a longer disease duration in the epsilon 4 allele carriers. After 3 years, MMSE test scores were still not significantly different between epsilon 4 carries and non-carriers but more than twice as many non-carriers had died. All other clinical features were similar between epsilon 4 allele carriers and non-carriers. This study indicates that the epsilon 4 allele is associated with a better prognosis of the disease in late-onset AD but that there are probably factors other than the epsilon 4 allele that are important for the AD phenotype.