OBJECTIVE: To assess the influence of socio-economic factors on breast cancer survival in Sweden, a country with population-based mammography screening and a uniform health care system aiming to provide care to all on equal terms. METHODS: All women with a first diagnosis of invasive breast cancer in Sweden in 1993 were identified in the Swedish Cancer Register. Their sociodemographic characteristics were determined by record linkages to the 1970, 1980, 1985 and 1990 Census databases, and a nationwide Fertility Register. Information on tumor characteristics at diagnosis was obtained from five Swedish Regional Cancer Registers. Survival status on 31 December 1998, was assessed through follow-up in the Swedish Cause of Death Register. RESULTS: Of totally 4645 eligible women diagnosed with breast cancer in 1993, 772 had died from breast cancer through 1998. After adjustment for tumor characteristics and age, risk of death was 37 higher among women of low compared to high socio-economic status (HR high vs. low 0.73; 95 CI: 0.54-0.99). This difference was most pronounced in women less than 50 years at diagnosis. CONCLUSIONS: These results show that socio-economic disparities in breast cancer survival prevail even in this relatively homogenous society, offering outreach mammography and standardised treatment regimens in a tax-funded health care system.