Crude and relative survival rates were analyzed using data from 4,199 incident breast cancers in females and 39 breast cancers in males registered between 1974 and 1988 in the Cancer Registry of the Swiss Canton of Vaud. The relative survival rates were 0.94 for females and 0.95 for males at 1 year, 0.87 and 0.95 at 2 years, 0.71 and 0.75 at 5 years, and 0.57 and 0.65 at 10 years. In relation to age at diagnosis, among females the relative survival increased from 0.62 for cases diagnosed under the age of 35 years to 0.78 at the age of 45-49 years, decreased to 0.66-0.68 in the age group 50-59 years, and rose again to reach 0.76 at the age of 65-69 years, declining thereafter to 0.69 at the age range 80-84 years. This pattern was already evident during the first 2 years of follow-up and persisted up to 10 years after diagnosis, although somewhat less defined. For males, no significant difference was evident in relative survival between breast cancers diagnosed before or at the age of 65 years and over, and only the 10-year survival rate was apparently (though not significantly) lower at older ages. Thus, these population-based data show remarkable similarities in survival for female and male breast cancer, despite possible heterogeneities in diagnosis and ascertainment of the disease as well as differences in steroid hormone levels in the two sexes and possible differences in biological characteristics of the disease. Further, they confirm that breast cancer survival varies across subsequent age groups. This possibly reflects selection and modifying effects on incidence and survival of hormone dependency of a proportion of breast cancers, the growth of which could be accelerated during the premenopause and the survival favourably influenced by the decline in steroid hormone levels after the menopause.