Enrollment in high-deductible health plans (HDHPs) has greatly increased in recent years. Policy makers and other stakeholders need the best available evidence about how these plans may affect health care cost and utilization, but the literature has not been comprehensively synthesized. We performed a systematic review of methodologically rigorous studies that examined the impact of HDHPs on health care utilization and costs. The plans were associated with a significant reduction in preventive care in seven of twelve studies and a significant reduction in office visits in six of eleven studies—which in turn led to a reduction in both appropriate and inappropriate care. Furthermore, bivariate analyses of data extracted from the included studies suggested that the plans may be associated with a reduction in appropriate preventive care and medication adherence. Current evidence suggests that HDHPs are associated with lower health care costs as a result of a reduction in the use of health services, including appropriate services.