Laboratory test method validation typically refers tothe multi-tiered process of evaluating the performance of a new instrument or test methodology, often in relation to an instrument or methodology that is currently in use. In its broadest sense, method validation comprises the evaluation of test performance following a change in reagents, instruments, methodology, or-unique to veterinary clinical laboratories—introduction of a new species. The ultimate goal of method validation is to provide objective evidence that the evaluated method will show acceptable reproducibility and accuracy so as to be clinically applicable. Consultation between a clinical laboratory and clinicians is often necessary to determine the acceptability of the data generated; successful test validation produces a reference interval, test sensitivity and specificity, or receiver operating characteristic curve that is medically useful. In the age of point-of-care instrumentation, issues of quality control and test validation are no longer restricted to clinical laboratories, but now fall upon the responsible clinician. The purposes of this article are to present a brief introduction to the concept of test method validation, to describe basic methods of validation, and to provide the clinician with a sense of the importance of test validation with respect to nonconventional species.