Arachidonoyl 2-chloroethylamide (ACEA) is a potent and selective cannabinoid (CB) receptor 1 agonist with Ki values of 1.4 and >2,000 nM for CB1 and CB2 receptors, respectively. In whole animal experiments, ACEA induces hypothermia in mice with the same efficacy as arachidonoyl ethanolamide , in spite of its higher affinity for the CB1 receptor. These data have been interpreted to indicate that ACEA may be a substrate for fatty acid amide hydrolase (FAAH), and thus only transiently available in whole animal experiments.