CMC studies are performed both during development of a pharmaceutical product or assay, as well as post licensure to guide decision making. Key to the implementation of these studies is a prescribed acceptance criterion associated with study outcome. Statisticians play a role in designing the study and analyzing the study data, and sometimes consult on the formulation of the acceptance criterion. Care must be taken in postulating the acceptance criterion, to identify and acknowledge the “customer”, and the risks and consequences of meeting or failing to meet the criterion. This presentation will compare and contrast bases for acceptance criterion in CMC studies, including studies related to patient safety and efficacy, process and analytical performance, and quality control.