A retrospective analysis of data from oral fluid specimens was conducted in order to identify a relevant cutoff concentration for opiates and/or synthetic opiates in oral fluid. Previously proposed regulations from the Substance Abuse and Mental Health Services Administration (SAMHSA) have recommended 40 μg/L as a cutoff concentration. In this study, data from oral fluid specimens collected using the Quantisal™ device and screened with enzyme linked immunosorbent assays (ELISA) for both opiates and oxycodone were retrospectively assessed for screen positives > 20 μg/L and those between negative and 20 μg/L. Specimens identified at these concentrations were then analyzed using liquid chromatography with tandem mass spectral detection using a fully validated procedure. Overall, 156 positive specimens were identified using 40 μg/L; 191 specimens using 20 μg/L; and 241 specimens between negative and 20 μg/L. Specifically, the number of 6-acetylmorphine (6-AM) positives increased from 10 to 16; morphine 4 to 9; codeine from 11 to 19; oxycodone from 56 to 74; hydrocodone from 73 to 119; and hydromorphone from 2 to 4 when specimens with enzyme inhibition between negative and 20 μg/L were analyzed. For workplace testing where only codeine, morphine, and 6-AM are considered, the use of a lowered cutoff concentration produced significant increases in the positive rate.