A sample of 1070 elderly persons aged over 65 living in the Liverpool community was interviewed using the community version of the Geriatric Mental State (GMS) and the findings processed to provide a computerised diagnosis by AGECAT. Levels of organic disorder, probably dementia, reached 5.2%, intermediate between those of London and New York derived from previous studies. Levels for depressive illness overall were below those of other studies at 11.3% while levels for neurotic disorder were much the same at 2.4%. The rise in the prevalence of dementia with age was further confirmed. The GMS AGECAT Package provides a method for standardising both the collection of data and the diagnostic process for comparative epidemiological studies and other research.