BACKGROUND: The aim was to investigate compliance by ethnic groups to the mammography screening programme in the City of Copenhagen over six years and to look at developments over time. MATERIAL AND METHODS: Mammography screening has, since 1 April 1991, been offered free of charge to all women between 50 and 69 years of age in the City of Copenhagen. Data on women born in Poland, Turkey, Yugoslavia, and Pakistan divided into five-year groups were compared to that of women born in Denmark and all other foreign-born women. Data from 1991 to 1997 were grouped according to the mammography performed, the offer refused, or non-appearance. RESULTS: Whereas 71% of Danish-born women accepted mammography, compliance by foreign-born women was significantly lower. The offer was accepted by 36% of Pakistanis, 45% of Yugoslavians, 53% of Turks, and 64% of Poles. Compliance fell in all ethnic groups with advancing age. Of the Danish women, 16% failed to keep the appointment. The corresponding percentages were 52 for Pakistanis, 48 for Yugoslavians, 41 for Turks, and 23 for Poles. The proportion of women who actively refused the offer was similar in all groups. The number of invited women fell during the period. CONCLUSIONS: The lower participation of women from the countries under study might have various explanations: among them the language barrier, procedure-related factors, and a lower incidence of breast cancer in the countries of origin.