Biokinetic modeling provides a mathematical technique for estimating absorption, distribution, metabolism, and excretion of chemicals, including particles and metals, in humans. Such models can be used to relate the amount of lead external exposure to the amount of lead found in the blood and other tissues at different points in time. At the request of the Department of Defense (DoD), Review of the Department of Defense Biokinetic Modeling Approach in Support of Establishing an Airborne Lead Exposure Limit evaluates whether the model used by DoD to derive airborne lead concentrations from blood lead levels is appropriate. This report also considers whether DoD's modifications to the model are appropriately justified, and whether the assumptions in and inputs to the model are reasonable.