The trend in the prognosis for female breast cancer patients was investigated by comparing Kaplan-Meier survival curves of different patient cohorts diagnosed during the period 1948-87. The study is based on 71,448 patients from the Danish Cancer Registry. The cohorts were defined by age at diagnosis, year of diagnosis, and residential area. The survival time from diagnosis nearly doubled from 1948-57 to 1978-87, the most important improvement taking place after 1978. Patients diagnosed in 1948-77 in the Copenhagen area had a far better prognosis than patients diagnosed during this period in other parts of Denmark. For patients diagnosed in 1978-87 the prognosis, however, reached an equal level in all parts of the country. Thus, it is reasonable to assume that the national programme introduced in 1977 by the Danish Breast Cancer Cooperative Group (DBCG) has played an important role and not only brought about therapeutic improvements in breast cancer treatment in Denmark, but also ensured equity in the outcome on a national scale.