OBJECTIVES: To examine the association of socio-economic position (SEP) with the diagnosis, treatment and control of diabetes, and with survival in women with and without Type 2 diabetes. METHODS: Prospective cohort study of 4277 women from 23 centres in Great Britain, aged 60-79 years at baseline. RESULTS: Of the 4277 women, 220 (5.1%) were known to have Type 2 diabetes and a similar number [n = 188 (4.4%)] had undiagnosed diabetes based on a single fasting glucose level > or = 7.0 mmol/l. Neither childhood nor adult SEP was associated with being correctly diagnosed amongst the 408 women with either diagnosed or undiagnosed diabetes. In both women with and without diabetes, SEP was associated with more adverse levels of fasting insulin, triglycerides, high-density lipoprotein cholesterol and body mass index, but was not associated with glycated haemoglobin in either group. Over the follow-up period, 395 women died. The hazard ratio for all-cause mortality per additional indicator of adverse SEP in adulthood in women with diabetes [1.40 (1.05, 1.85)] was similar to that in women without diabetes [1.26 (1.12, 1.41], P for difference in the two estimates = 0.70). Childhood SEP was not associated with survival. CONCLUSION/INTERPRETATION: A considerable number of older women with Type 2 diabetes are not diagnosed, but SEP is not related to being correctly diagnosed. The marked socio-economic gradient for all-cause mortality is the same for women with and without diabetes and is not fully explained by conventional risk factors.