U.S. policymakers have relied on offsets from developing countries as a primary form of cost containment in proposed cap-and-trade legislation. These legislative proposals allow for emitters to use up to 1.5 billion tons CO2e of offsets from developing countries to meet their annual compliance obligations. This paper review estimates of the projected availability (i.e., supply) of international offsets, and evaluate the various methods used. This paper outlines factors that should be incorporated into future analyses of international offset supply and quality. Such analyses could prove particularly germane as policy makers continue to deliberate on the role of international offsets, including whether and how to recognize credits from the Clean Development Mechanism (CDM), develop new sectoral crediting mechanisms, and consider offsets for reduced deforestation.