Incurred Sample Reproducibility (ISR), also called Incurred Sample Reanalysis, has been a primary testing requirement according to FDA and EMA regulatory guidance since approximately 2008. The Bioanalytical laboratories conducting these tests have accumulated a significant body of experience in running ISR, performing investigations into ISR failures, and developing an understanding of the impact of ISR data. In this Webinar, ISR fundamentals (What is it and how does it affect my program?) will be discussed with the Study Direct/Toxicologist in mind. Case examples of ISR failure will be presented along with interpretation and impact to TK data as well as an overall assessment of toxicological study impact.