Summary: Pursuant to a congressional request, GAO reviewed employer association health care plans and state regulation of these plans. GAO noted that: (1) identifying association health plans is difficult because there is no common industry or statutory definition of them; (2) association health plans and similar purchasing alliances account for about 17 percent of the national small employer insurance market; (3) market penetration varies by state due to differences in states' definitions and regulation of such plans; (4) broad statutory language has led to regulatory confusion in 27 states as to how to categorize a particular plan; (5) in determining how association health plans are to be regulated, states need to determine whether such plans cover individuals as well as small firms, the plans are fully insured or self-funded, and self-funded plans are subject to state regulation as multiple employer welfare arrangements or are exempt from state regulation; and (6) state regulators are concerned that some association plans that are domiciled in one state, but operate in multiple states, may be using state law ambiguity to avoid state regulation.