The apolipoprotein E gene has been associated with various types of dementia. We studied the connection between the APOE gene and the risk and onset of disease in 34 patients with clinically diagnosed frontal lobe dementia (FLD) derived from a population-based study in the Netherlands. A significant increased risk of FLD (odds ratio, 4.9; 95% CI, 1.1-20.1) was found for the apoE4E4 genotype when adjusting for age, sex, and family history of dementia other than FLD. The age at onset of the disease decreased as the number of APOE*4 alleles increased. Our population-based study suggests that persons who are homozygous for the APOE*4 allele are at increased risk for developing FLD.