This paper is a comparative analysis between the application of the FDA Process Validation Guidance (2011) to new products and legacy products. While the three stages of process validation (design, qualification, and continued monitoring) provide a clear framework for the development, scale-up, qualification, and manufacturing of new commercial products, the application of these process validation principles to legacy products is only briefly mentioned in the FDA guidance. A practical approach, which applies analysis of historical data, risk assessment, and statistical principles, is outlined for legacy products in order to assess whether these existing processes require further supporting experimental and qualification activities…