The number of people enrolled in consumer-directed health plans (CDHPs) has increased dramatically over the last decade. We reviewed the empirical literature on the effects of CDHPs, which is based on the experience of these plans in the employer-sponsored market. Studies indicate that CDHPs reduce health care spending by approximately 5-15 percent relative to similar plans with lower deductibles and without spending accounts. Spending deductions are concentrated amoung healthier enrollees and are driven by reductions in the use of outpatient services and pharmaceuticals. There is little evidence on whether they reduce the use of low-value services.