The Mental Health Parity and Addiction Equity Act (MHPAEA) mandates equity in insurance coverage, including both treatment limits (caps on inpatient days and outpatient visits) and financial requirements (cost sharing, deductibles, and out-of-pocket limits), for behavioral health and medical/surgical services. Some insurers and employers, however, have voiced concerns that implementation of the MHPAEA will lead to larger cost increases than those found in previous studies of parity. Generally, these studies have found that parity can be achieved with few if any increases in total health care costs (1). The new federal law goes further than most previous laws by extending parity to managed care techniques that may not be expressed numerically but may nevertheless limit the scope or duration of services—so-called nonquantitative treatment limitations. These management techniques include requirements such as prior authorization, utilization review, or standards for provider participation in a network. Under the new federal law, insurance plans must use the same processes or strategies that they use for medical/surgical benefits to determine how nonquantitative treatment limitations are set. Because some studies suggest that these management techniques are what allowed parity to occur without large cost increases in the past (2), there are concerns that the new federal law would lead to relatively large cost increases. However, there is no published direct evidence to date on the effect of the MHPAEA on health care costs.