The aim of the present study was to develop and validate a method for the detection and quantitation of drugs of abuse in oral fluids. Fortified oral fluid samples (made in-house) and samples from donors collected with Quantasil oral fluid collection kits from Immunalysis were screened on an Olympus 5400 using reagents purchased from Immunalysis. Amphetamines (AMPs), opiates, phencyclidine (PCP), and cocaine and its metabolite benzoylecgonine (BE) in oral fluids were quantitated by an Applied Biosystems 3200 QTRAP liquid chromatograph-tandem mass spectrometer (LC-MS-MS). AMPs, opiates, PCP, cocaine, and BE were extracted from samples using liquid-liquid or solid-phase extractions and the extracts were separated on a Shimadzu high-performance liquid chromatograph prior to the MS-MS analysis. For each drug, two multiple reaction mode transitions were monitored using positive electrospray ionization coupled to an MS-MS detector. Corresponding d3, d5, d6, and d11 internal standards were used to quantitate the results. The limit of detection/quantitation for AMPs, opiates, PCP, cocaine, and its metabolite BE were 10, 10, 2, 2, and 2 ng/mL of oral fluid, respectively, on a signal-to-noise ratio > 4. This corresponded to 25, 25, 5, 5, and 5 pg on column. The method was verified by participating in the North America Oral Fluid Proficiency Testing administered by Research Triangle Institute and by analyzing real samples from donors. In conclusion, LC-MS-MS provided a simple way to analyze and quantitate drugs of abuse in oral fluids.