Synthetic cathinones are a new class of designer drug derived from khat (Catha edulis), a shrub native to Africa and the Arabian peninsula. Chemically, they are phenethylamine derivatives with a ketone at the ß-carbon. Due to their amphetamine-like structure, the drugs can be classified as sympathomimetic amines. However, synthetic cathinones can produce a complex array of adrenergic and serotonergic effects, and the combination of stimulant and moodaltering sensations have contributed to the popularity of these substances among recreational drug users. Despite the federal government exercising its emergency scheduling authority late in 2011, and enactment of the Synthetic Drug Abuse Prevention Act of 2012, which permanently scheduled two synthetic cathinones, manufacture and distribution continue to circumvent regulation and enforcement efforts. There have been numerous reports of impaired driving, fatal intoxications and adverse consequences following the use of these drugs. Quantitative drug toxicology, typically in blood, but also in other tissues or fluids, may be used interpretively by a toxicologist. However, changes in concentration, such as those that may occur due to instability or during storage, transportation, or during human decomposition, may influence these opinions. A very limited number of published reports suggest concern regarding the stability of some, but not all of the synthetic cathinones. Degradation has been reported for mephedrone in aqueous media. Sample losses of >50% were reported for mephedrone in whole blood stored at 4°C in blood for 14 days (Johnson and Botch-Jones, 2013). All preliminary work published to date calls for additional study. To date, there have been no systematic studies regarding the stability of synthetic cathinones in biological evidence. Since this class of drug is rapidly changing and new analogs are inevitable, it is important to understand specifically which chemical characteristics contribute to stability, so that this knowledge can be applied to future analogs that will inevitably make their way into the illicit drug market. The purpose of the study is to evaluate the stability of synthetic cathinones in toxicological samples. More than twenty target analytes have been tentatively identified, and these include several commercially available metabolites. Stability will be evaluated at four temperatures (-10, 4, 20 and 32°C ) for a period of no less than six months. Blood and urine will be investigated, and based on preliminary data that suggests that degradation may be pH dependent, urine will be investigated at pH 4.5 - 8.0. The most widely used cathinones will be selected for study, and those that allow for structural inferences to be made concerning the stability of future analogs; specifically those with a variety of benzylic and amine (primary, secondary and tertiary) substituents. All quantitative measurements will be made using liquid chromatography-tandem mass spectrometry (LC/MS/MS). Solid phase extraction (SPE) and LC/MS/MS will be used for isolation and identification purposes for all target drugs. The analytical procedure will undergo full scientific validation in conformance with recently proposed guidelines from the Scientific Working Group on Toxicology and generally accepted practices in accredited laboratories under ISO/IEC 17025. In addition to the investigation of chemical instability using fortified biological matrices, authentic case samples will be reanalyzed after a period of storage under specified conditions. The comparison of results using authentic samples, retested after storage, with initial results reported by an accredited laboratory, will afford the opportunity to confirm the experimental observations made using fortified samples. Additionally, methodology developed for simultaneous determination of the target analytes will benefit laboratories attempting to broaden the scope of their analyses.