EPA is approving a State Implementation Plan (SIP) revision submitted by the State of Maryland on April 27, 2000. This revision was submitted to satisfy EPA's regulation entitled, "Finding of Significant Contribution and Rulemaking for Certain States in the Ozone Transport Assessment Group Region for Purposes of Reducing Regional Transport of Ozone," otherwise known as the "NO<INF>X</INF> SIP Call." This revision establishes and requires a nitrogen oxides (NO<INF>X</INF>) allowance trading program for large electric generating and industrial units, and reductions for cement kilns and stationary industrial combustion engines, beginning in 2003. The intended effect of this action has two purposes. EPA is approving the Maryland's NO<INF>X</INF> Reduction and Trading Program because it meets the requirements of the NO<INF>X</INF> SIP Call that will significantly reduce ozone transport in the eastern United States. In addition, EPA is approving Maryland's NO<INF>X</INF> Reduction and Trading Program because it supports the one-hour attainment demonstration plans for the Baltimore, Metropolitan Washington, D.C. and Philadelphia-Wilmington-Trenton ozone nonattainment areas.