This paper evaulates documentation and research published and available for the two commercial fentanyl assays currently available on the market: the ARK Fentanyl II Assay/DRITM Fentanyl Assay and the Fentanyl Urine SEFRIATM by Immunalysis. Comparisons of clinical sensitivity, specifity and robustness, and precision/reproducibility reveal a clear leader in the DRI Fentanyl Assay.