The DJ-1 gene is associated with autosomal recessive early-onset Parkinsonism, most likely through its role in defense against oxidative stress. Oxidative stress is not only involved in Parkinson's disease, but also in other neurodegenerative disorders, such as dementia. We assessed the presence of a 14 kb DJ-1 deletion in 191 patients with dementia, ascertained from the genetically isolated population where the first kindred with DJ-1 related Parkinsonism was originally identified. The control group consisted of 129 non-demented subjects. We found the deletion in two patients and one control. There was no evidence for an increased risk of dementia in carriers. All subjects were heterozygous for the deletion and related to a common ancestor within eight generations. Our results suggest it is unlikely that haploinsufficiency in the DJ-1 gene imparts an increased risk for dementia.