Background Equity of service provision by age, ethnicity and sex is a key aim of Government policy in the UK. The prevalence, natural history and management of common chronic conditions, such as diabetes and hypertension, vary between ethnic groups. Developing and monitoring responsive local services requires accurate measures of ethnicity and language needs. Hence establishing the ethnic composition of GP populations is important. Objective To compare three methods of estimating the ethnic composition of GP registered populations in three east London primary care trusts (PCTs). Design Self-reported ethnicity, routinely collected at practice level (and considered the 'gold standard'), was compared with two indirect methods of attributing ethnicity. The indirect method currently used in the UK assigns ethnicity to GP populations based on geographical postcode attribution from the national census. A proposed alternative indirect method uses the ethnic breakdown of hospital admission data from practice lists to attribute ethnicity to the whole practice population. Comparisons were made between practice self-report recording and these two indirect methods. Bland-Altman plots