Forces of change in the health care system. Implications for cancer care in the 1990s. Dramatic changes will occur in the health care system during the 1990s which will profoundly affect the delivery of care for cancer. Perhaps the most important factor is the aging of the population. As the proportion of people who achieve old age increases, the absolute prevalence and incidence of cancer will increase despite improved treatment techniques. This phenomenon will increase health care expenditures despite ongoing efforts to control costs. Second, there will be continuing efforts at cost control and increased emphasis on quality assurance and outcomes by third party payers. Providers will be scrutinized and compared with one another. The large payers of the nation's health care bills will demand proof of outcome and cost leading to bidding by providers and payment only to those who have the best outcome for the least money. Third, there will be an increasing emphasis on prevention and screening, in public health policy, an approach that may conflict with personal freedom. Fourth, there will be increasing deliberations and questions about the ethics of the health care system and treatment decisions. There will be continuing debate about the need for a rationing of health care and the right of individual privacy versus the states' right to preserve life. These changes will impact on all health care professionals whose practice includes patients with cancer. 