The study aim is to measure possible differences in access to health care among immigrant women with breast cancer compared with Danish women. We used tumour size at diagnosis as a proxy measure of access. The Danish Central Personal Register provided information from 1977-1996 on women between 20-75 years born in countries in which Islam is the dominating faith. These data were linked to the Danish Breast Cancer Cooperative Group, which registers data concerning tumour size. Sixty-five immigrant women with breast cancer were identified and matched with a control population of Danish women. The study showed larger tumours at diagnosis among women from ethnic minority groups compared to Danes. However, this tendency was not significant. Furthermore, mammographic screening had a significant effect on the tumour sizes of Danish women, but not on those of immigrants. The study indicates ethnic inequalities related to access to health services as measured by tumour size.