A study was conducted to assess the impact of three anticipated changes in the health care system on the future requirements for registered nurses. The changes investigated were the introduction of national health insurance (NHI), the increased enrollment in health maintenance organizations (HMOs), and the reformulation of nursing roles. Following a literature search which revealed that no single previous study provided significant information on the research problem, a model was developed to predict nursing manpower requirements in relation to the projected population of health consumers and the determination of its demands for health services. Based on the estimates obtained from the model's application, it was concluded that (1) of the three changes studied, future growth in HMO enrollments is the least significant; (2) if neither of the two major changes occurs, the requirements for nurses will increase by approximately 145 percent from 1972 to 1985; and (3) for either of these two changes separately, an additional increase of seven to fifteen percent is expected, while for the two combined, an extreme projection of up to an additional fifty-three percent can be made. Preliminary comparisons of these estimated increases with available supply estimates of nurses showed no alarming imbalances, although the passage of NHI without sufficient advance preparation could produce a higher demand than supply. (ELG)