As a result of various proposals currently under consideration by EPA, it seems highly likely that many stationary sources of greenhouse gas emissions will face new regulation under the Clean Air Act in coming months. Since applicability of the PSD and Title V programs is, at least in EPA's eyes, driven by the adoption of any form of greenhouse gas emissions control, sources of greenhouse gas emissions may be subject to these programs as soon as EPA finalizes its light-duty vehicle greenhouse gas regulation, which is expected in March 2010. Companies and other regulated entities, therefore, should begin preparing for this outcome, while simultaneously taking whatever measures they deem necessary to continue to influence the rulemaking process. These opportunities still exist with proposals still subject to public comment. However, the time for acting is diminishing quickly.