Marijuana is a commonly abused drug because of its central nervous system depressant effects and its hallucinogenic properties. The primary pharmacologically active component in marijuana is ∆9-tetrahydrocannabinol (THC). The pathway for metabolism and excretion of THC leads primarily to the formation of 11-hydroxy-∆9-tetrahydrocannabinol (THCoh), which further metabolizes to 11-nor-∆ 9-tetrahydrocannabinol-9-carboxylic acid (THCc) (1). Unchanged THC exists in urine in only trace amounts, and THCoh accounts for only 2% of the excreted dose (2). The detection of THCc and its conjugates, which are the major urinary metabolites of THC, is also important in determining exposure to marijuana. The detection of THC in blood is important in human performance and postmortem toxicology in order to correlate recent drug use with impaired performance or behavior. Detection and quantification of low blood concentrations of THC are required because of THC’s short half life and the time gap that occurs between the collection of the specimen and the human performance event. Because of marijuana’s popularity and frequency of abuse, forensic toxicology laboratories must have a rapid, sensitive, and inexpensive method for determining the presence of major marijuana constituents in biological specimens. In addition, Ohio Department of Health (ODH) regulations require all laboratories in Ohio to report concentrations of THC and THCc in blood specimens down to 2 and 5 ng/mL, respectively, and 15 ng/mL THCc in urine. Methods consisting of liquid–liquid and solid-phase extraction (SPE) have been published (3–20). These methods focus primarily on the separation of acidic and basic fractions, resulting in two separate chromatographic analyses for THC and THCc.