OBJECTIVE: To assess the associations between childhood and adulthood social class and insulin resistance. DESIGN: Cross sectional survey. SETTING: 23 towns across England, Scotland, and Wales. PARTICIPANTS: 4286 women aged 60-79 years. MAIN OUTCOME MEASURES: Insulin resistance and other cardiovascular disease risk factors. RESULTS: Belonging to manual social classes in childhood and in adulthood was independently associated with increased insulin resistance, dyslipidaemia, and general obesity. The association between childhood social class and insulin resistance was stronger than that for adult social class. The effect, on insulin resistance and other risk factors, of belonging to a manual social class at either stage in the life course was cumulative, with no evidence of an interaction between childhood and adult social class. Women who were in manual social classes in childhood remained at increased risk of insulin resistance, dyslipidaemia, and obesity--even if they moved into non-manual social classes in adulthood--compared with women who were in non-manual social classes at both stages. CONCLUSIONS: Adverse social circumstances in childhood, as well as adulthood, are strongly and independently associated with increased risk of insulin resistance and other metabolic risk factors.