The purpose of the study was to estimate the risk of one-year incident dementia in elderly community dwellers, according to their performance on a four Instrumental Activities of Daily Living (IADL) score. From a random sample of 2792 French elderly community dwellers included in the PAQUID study, 1804 non-demented subjects were interviewed by specifically trained psychologists about their performance on telephone use, use of transport, responsibility for medication intake, and budget management, and then followed up. One year later 21 of these subjects had a diagnosis of incident dementia, according to DSM-IIIR criteria and confirmed by a neurologist. The odds ratio for incident dementia, adjusted for age, increased from 10.6 for subjects dependent in one IADL to 318.4 for those dependent in the four IADLs (p < 0.0001), compared with independent subjects. These four IADLs could be useful for screening subjects at high risk of incident dementia.