Summary: Pursuant to a congressional request, GAO provided information on state regulation of health plans, particularly mandated health insurance benefit laws. GAO noted that: (1) the number and type of mandated benefits vary by state, but they range from 6 to 39 and average 18 per state; (2) states most frequently mandate the coverage of preventive care and some states mandate coverage of services by nonphysician providers; (3) assessing the impact of mandated benefits is difficult because each benefit varies depending on state law and employer practices; (4) studies have shown that mandated-benefit costs vary by state, ranging from about 5 percent to 22 percent of claims costs; (5) mandated-benefit costs are generally higher in states with more mandated benefits and higher-cost mandated benefits; (6) mental health and substance abuse services are the most expensive benefits; and (7) self-funded health plans often cover commonly mandated benefits, even though they are exempt from state regulation, and there is little difference in claims costs between self-funded and fully-insured heath plans.