The authors' interest was focused on the direct determination of differences between the salient features of breast cancer in men and women in a large number of patients. Various epidemiological features were analyzed in a group of 386 male and 21,491 female breast cancer patients registered in the Cancer Registry of the Republic of Croatia from 1968 until 1988. This was a population-based study, and all male and female breast cancer cases recorded during the mentioned period were included in the study. During this 21-year period, the total incidence rate of breast cancer in men was about 0.83/100,000, and the mortality 0.2,/100.000. In the same interval, in women the rates doubled from 30 to 60/100,000, and 13 to 29/100,000, respectively. The highest incidence rates were recorded in the 80-84 age group in men, and 60-64 age group in women. The mean age at diagnosis was 63.4 years in men and 58.2 years in women. The distribution in terms of TNM-stages in men was: stage I-10.10%; II-40.67%; III-32.40%; IV-16.83%; in women; I-12.19%; II-49.36%; III-27-58%; IV-10.86%. The results showed that breast cancer in men had epidemiological characteristics of a sporadic disease, occurring continuously at a specific mean frequency in the general population and being little affected by environmental impacts. Conversely, in women affected by the disease there was a tendency of continuous rise in the morbidity and mortality, which might have been due to the trigger action of one or more environmental factors.(ABSTRACT TRUNCATED AT 250 WORDS)