Inheritance of the apolipoprotein E (ApoE) ϵ4 allele is a risk factor for Alzheimer's disease (AD) and is associated with increased deposition of β-amyloid (Aβ) in AD, Down's syndrome, and normal aging. Aβ deposition in the form of senile plaques (SPs) has recently been described in patients with temporal lobe epilepsy (TLE). We studied the relationship between ApoE ϵ4 genotype and the deposition of Aβ in temporal lobe tissue from patients who underwent temporal lobectomy for intractable epilepsy. TLE patients with SPs had a 70% ApoE ϵ4 carrier frequency compared with a 27% carrier frequency among age-matched TLE controls without SPs. Our data suggest that the association between ApoE ϵ4 and intracerebral Aβ accumulation is not unique to the elderly or to those with dementia, and may be a feature of conditions in which there is both an ApoE ϵ4 allele and over-production of Aβ precursor protein, and, presumably, Aβ.