Value-based insurance design (VBID) is an approach that attempts to improve the quality of care by selectively encouraging or discouraging the use of specific health care services, based on their potential benefit to patients' health, relative to their cost. Lowering beneficiary cost sharing or out-of-pocket spending to increase medication adherence is one common element of value-based insurance design. We conducted a systematic review of the peer-reviewed literature to evaluate the evidence of the effects of VBID policies on medication adherence and medical expenditures. We identified thirteen studies assessing the effects of VBID programs and found that the programs were consistently associated with improved adherence (average change of 3.0 percent over one year), as well as with lower out-of-pocket spending for drugs. In the studies we reviewed, providing more generous coverage did not lead to significant changes in overall medical spending for patients and insurers. Further research is needed to understand how best to structure VBID programs to both improve quality and reduce spending.