A joint Nordic study was conducted to elucidate the survival pattern in male breast cancer by means of regression analysis of annual relative survival rates. A total of 1429 (98.4%) of all patients diagnosed during a 25-year to 30-year period and reported to the Nordic cancer registries were available for follow-up through 1982. The relative survival rate was lower in older patients; the relative excess risk of dying (from breast cancer) during the first 5 years of observation, calculated by multiple regression modelling, increased in a regular fashion more than three-fold from patients younger than 40 years at diagnosis to those aged 80 years or older. Significantly lower rates were found among males in Denmark and Finland, the relative excess risks of dying (compared with Sweden) being 1.39 (1.06-1.80) and 1.73 (1.22-2.45), respectively, during the first 5 years. The authors concluded first that important differences exist between male and female patients with breast cancer in the relation between survival and age at diagnosis, and secondly that a later stage at presentation or national differences in the natural history are the most likely explanations for the worse prognosis in Denmark and Finland.