This paper considers the use of small area census data in deriving socio-economic health need indices for primary care practices and assesses how far such indices are related to practice activity. A particular goal is the derivation of weightings for resourcing formulae which incorporate the effect of socio-economic deprivation on activity as well as the more usual allowance for patient age alone, so ensuring a closer match between needs and resources across both practices and localities. A case study is undertaken of a health authority in East London with a population of 380 thousand and 97 primary practices. Total rates of inpatient and outpatient referral and of prescribing by practices all show an influence of practice deprivation after allowing for age, and this effect is enhanced for subcategories such as emergency referrals to A&E departments. After taking account of practice age structure and deprivation, practice characteristics themselves (e.g. number of GPs in relation to practice population) are relatively unimportant influences on activity. The paper discusses how variation in need may be incorporated into resourcing via differential weighting.