Trends for female breast cancer were examined by age, period and cohort for the years 1950-1984 in U.S. mortality. Connecticut mortality and Connecticut incidence. Birth cohort patterns were evident for all three sets of data. The results confirm a continuing increase in invasive breast cancer by providing evidence of a strong birth cohort pattern, over a time series of 90 years of birth cohorts. This trend appears to be real for the most part because of the cohort patterns and because there is minimal underdetection in data obtained by autopsy and blind biopsy. Secondly, when cohort modeling is applied to breast cancer mortality, there is an indication of a modest decline in recent breast cancer mortality (in the face of an apparent long-term increase), which suggests that control of breast cancer mortality may have developed in recent decades, perhaps through earlier detection and improved treatment. Finally, in contrast with a prior report, there is little evidence for a clinically important difference in time trend between pre- and postmenopausal breast cancer.