Breast cancer is the second leading cause of death by cancer among women in the United States. The total cost of illness for breast cancer has been estimated to be $3.8 billion, of which $1.8 billion represents medical care costs. It has been estimated that breast cancer detected early is considerably less expensive than when the tumor is discovered at a later stage. Mass screening using mammography can improve early detection by as much as 15-35%. Cost-effectiveness studies have estimated that the costs of breast cancer screening range between $13,200 and $28,000 per year of life saved. The cost-effectiveness of breast cancer screening in the 40-49-year-old age group is controversial. Mass screening for breast cancer will probably increase total health care costs, but when all economic costs are included, screening appears to be more cost-effective than not screening.