Enrollment is increasing in consumer-directed health insurance plans, which feature high deductibles and a personal health care savings account. We project that an increase in market share of these plans--from the current level of 13 percent of employer-sponsored insurance to 50 percent--could reduce annual health care spending by about $57 billion. That decrease would be the equivalent of a 4 percent decline in total health care spending for the nonelderly. However, such growth in consumer-directed plan enrollment also has the potential to reduce the use of recommended health care services, as well as to increase premiums for traditional health insurance plans, as healthier individuals drop traditional coverage and enroll in consumer-directed plans. In this article we explore options that policy makers and employers facing these challenges should consider, including more refined plan designs and decision support systems to promote recommended services.