Breast cancer mortality is declining in the United States, as well as in certain other industrialized areas--such as Canada, Austria, Germany, and the United Kingdom--possibly due to increased utilization of mammographic screening, early detection of disease, and availability of improved therapies. At least some of the decline has been attributed, however, to the higher fertility rates of the cohort of women born between 1924 and 1938 who bore children during the post-World War II period. In contrast, certain European nations--Spain, Portugal, Greece, Hungary, Poland, and Italy--have not reported these favorable trends. The lowest breast cancer mortality rates are reported in Asian regions, leading researchers to speculate that dietary, cultural, and/or environmental factors might be implicated in the etiology of the disease.