['To determine the frequency of unrecognised dementia in a group of community dwelling elderly, and to identify factors associated with dementia recognition by informants. SAMPLE SELECTION: People over 65 years with an AGECAT case or subcase organic diagnosis or an MMSE < or = 23 were identified from a database of community dwelling elderly. A psychiatrist to confirm the diagnosis of dementia according to ICD-10 criteria interviewed these individuals.', 'Sixty-two community dwelling elderly meeting ICD-10 criteria for dementia whom had reliable informants.', 'Prior to the start of the interview the informant was questioned about whether they felt the patient had memory difficulties and if so whether they had a medical evaluation for their memory problems. A psychiatrist then interviewed the patient and informant to establish whether that patient met ICD-10 criteria for dementia. Basic sociodemographic details were collected and the following assessments were carried out: the Blessed Dementia Rating Scale, the Clinical Dementia Rating Scale, the Behave-AD and the Baumgarten Behavioural Disturbance Scale.', 'Univariate and step-wise forward logistic regression analysis were used to examine the factors associated with recognition of memory difficulties.', "Twenty-nine percent of family informants of people with dementia failed to recognise a problem with their relatives'memory. Where memory difficulties were recognised only 39% of this group received a medical evaluation. Using univariate analysis recognition of memory difficulties by family informants was associated higher levels of behaviour disturbance ( p = or < 0.0011), greater functional impairment ( p = 0.0039), with increasing cognitive impairment ( p = 0.013). Using a logistic regression model, to test the independence of these variables, increasing behavioural disturbance (p = 0.0001) was associated with recognition of dementia by family informants."] Does behavioural disturbance trigger recognition of dementia by family informants?