Editors' Summary: The question of how to fairly apportion cleanup costs at Superfund sites is a highly debated topic in the law of hazardous substances. This Article highlights the deficiencies found in common allocation methods, and offers cost causation as a rational approach to apportioning cleanup costs. After providing a background on the CERCLA liability scheme, the authors address the various equitable factors used to apportion cleanup costs and discuss cost causation's relationship with those factors. The authors then introduce cost causation in an examination of how cleanup costs are created at a site and who is responsible for the specific costs. Next, they use figures and hypothetical scenarios to explain cost causation analysis and to note the deficiencies of volumetric- and toxicity-based allocations of costs. They conclude that although cost causation analysis may not address every equitable issue, it addresses many of them, and is flexible enough to incorporate others.