Editors' Summary: The CAA's PSD program is extraordinarily complex. This Article, written in two parts, focuses on the root of the PSD implementation process--baselines, increments, and ceilings. After exploring the essential features of baselines, increments, and ceilings, Prof. John-Mark Stensvaag delves into the complications that clutter up the theoretical simplicity of these features--complications flowing from statutory drafting, regulatory drafting, and interpretative choices made during the first 30 years of the program. Part I, presented below, examines the random, chaotic nature of the baseline date creation process. Part I also looks at baseline areas, which have a profound impact on when the baseline and ceiling concentrations are established and when the increment consumption clock begins to run. Despite the importance of this geographic PSD component, the CAA provides little guidance on the baseline area issue. Part II of the Article, which will appear in the January 2006 issue of News & Analysis, will examine baseline concentrations, ceilings, and increment consumption, and will provide the author's final thoughts and recommendations.