ABSTRACT The rapid growth trend of electronic equipment heat density is causing concern regarding how to cool these high@ if not extreme@ loads. Successfully cooling these loads is a complex problem that is made even more difficult by the lack of practical field experience with high density loads. High density loads amplify the impact on the cooling system of many variables (infrastructure configurations@ spatial allocations@ etc.) that previously may not have been the focus of the design engineer: The need for a solution is immediate@ but (due in part to the dot-com crash) there has been a lack of resources to proactively address the problem. Therefore@ the industry has fallen behind and requires accelerated recovery. The compounded effect of these issues creates a need for a more holistic approach than those previously utilized with a view to a coordinated process that results in planned solutions meeting the approval of all affected parties. The first step toward this holistic approach has been taken by ASHRAE TC9.9 with the publication ofThenna1 Guidelines for Data Processing Environments. Following on from that publication@ this two-part paper examines some of the topics that should be considered as a part of the holistic approach and provides some background on the high density cooling topic in general.