Implementation of the Single Assessment Process in the UK is designed to ensure that more standardized assessment procedures are in place across all areas and agencies, that practice improves and older people's needs are comprehensively assessed. This study provides a unique picture of the range and prevalence of standardized scales used within Old Age Psychiatry Services in England and Northern Ireland, reported by 73% of old age psychiatrists. Most services (64%) used three or more standardized assessment scales (range 1-12). Sixty-two separate instruments were identified. The six most used measures were the Mini Mental State Examination (95%), the Geriatric Depression Scale (52%) and the Clock Drawing (50%), the Clifton Assessment Procedures for the elderly (26%), the Barthel Index (18%) and the Health of the Nation Outcome Scales (HoNOS) 65 + (18%). A number of factors were associated with greater use of certain standardized assessment scales. Shared documentation, along with other indicators of integration between health and social care were associated with greater use of standardized scales. The provision of a memory clinic was associated with greater use of neuropsychiatric scales and lower levels of use of cognitive scales. These results provide key material for shaping the provision of psychiatric services for older people