Monoacylglycerol lipase (MAGL) hydrolyzes the endogenous cannabinoid 2-arachidonoyl glycerol (2-AG), terminating its capacity to activate cannabinoid receptors. Pristimerin is a naturally occurring terpenoid that potently inhibits MAGL (IC50 = 93 nM). Its actions are rapid, reversible, and noncompetitive. Pristimerin (1 μM) significantly increases 2-AG levels in isolated rat neurons, indicating that it inhibits endogenous MAGL in cultured cells. Moreover, it does not increase levels of palmitoyl ethanolamide, suggesting that pristimerin does not affect the activity of fatty acid amide hydrolase (FAAH).