When a toxic substance is released to the environment, it may not immediately reach and affect a population of sensitive receptors. This is particularly true if the substance must pass through a sequence of environmental compartments each of which causes a delay in the transfer process. Nevertheless, the act of introducing that substance into the environment constitutes on behalf of the receptors a commitment to a future exposure. The totality of that future exposure is called the exposure commitment. In this report, relevant concepts and the use of this approach to environmental assessment are discussed.