A Classification of Residential Neighborhoods (ACORN) and the Registrat General's social class classification were compared on measures of health and service use based on a sample of 5500 primary school children in England. ACORN was shown to differentiate at least as well as social class on the selected outcome measures and to identify small areas with particularly high rates of morbidity. Nevertheless, questions were raised concerning both the extent to which ACORN identifies variations independent of regional variations and the consistency of ranking of ACORN groups on health measures.