Background Due to the absence and or costliness of biological measures such as glycated haemoglobin, diabetes case ascertainment and prevalence studies are usually conducted using surveys or routine health service use databases. However, the use of each of these sources is associated with its limitations potentially impacting the quality of the case ascertainment and prevalence estimation. This study aimed at ascertaining diabetes cases and estimating prevalence among mid-and older-age women through simultaneous use of a longitudinal survey and multiple healthcare administrative data sources. Methods Data were available for 12,432 and 13,714 women born in 1921-26 and 1946-51 from the Australian Longitudinal Study on Women's Health (ALSWH). Diabetes was ascertained using the ALSWH survey, health service use, and cause of death data. Parsimonious multiple logistic regression analyses tested associations between sociodemographic and health variables and the presence of diabetes.