The residue analytical method is developed and used to quantify the individual components of the total toxic residue (TTR) present in food and feed RACs of crop and livestock samples. In order to provide assurance that the aged residues are completely accounted for in the residue analysis, the radioactive samples from the plant and livestock metabolism studies are extracted using the residue analytical method and the components of the TTR are quantified. The results from this radiovalidation study verify whether the extraction procedure of the residue analytical method is fully capable of extracting the aged residues in RAC samples. The regulatory agency requires that the applicant for the registration of the agrochemical should conduct radiovalidation study to determine the extraction efficiency of the residue analytical method and submit the results of the study with the registration data package for review by the agency. The chapter includes the description of a radiovalidation case study verifying that acceptable extraction efficiency for the residue components is achieved by the residue analytical method in the study.