Using data from the Surveillance, Epidemiology, and End Results (SEER) Program and the National Center for Health Statistics, trends in female breast cancer rates were examined for the time period 1973-1989 for the age group 20-39 and contrasted with those for older ages. Only about 7% of breast cancers occur by the age of 40; the risk of developing breast cancer prior to the age of 40 is less than 1%. The incidence trends for women in the 20-39 age group have been essentially stable, whereas for women 40 and older the rates increased steeply during the 1980s (at a faster rate than anticipated based on historical trends) and then leveled off beginning in 1987. Breast cancer mortality has been much more stable over time than incidence. Up to age 40, blacks have a higher incidence than whites. Over age 40, white rates exceed those for blacks, and the absolute and relative differences in incidence increase with advancing age. For whites, 5-year relative survival rates improved with advancing age up to age 50. Blacks under the age of 30 had survival rates similar to whites, whereas, in the older age groups, whites had somewhat better survival rates overall and by stage. The occurrence of second cancers was also analyzed in women with a first invasive breast cancer. Cancers found to occur at higher than expected rates included leukemia and cancers of the breast, ovary, and lung.