Increased reliance on pharmacokinetic studies in regulatory submissions emphasizes the need for cross-validating bioanalytical methods between different laboratories to allow comparison of data. Globalization of pharmaceutical development results in a greater need to define cross-validation standards. A strategy for performing cross-validation experiments using prepared biological samples of known concentration and "real" samples from clinical trials is presented. The statistical techniques used to compare data sets and establish acceptability of the assays are illustrated by practical examples.