Endogenous cannabinoids have been implicated in addictive behaviors and drug abuse. Fatty-acid amide hydrolase 1 (FAAH1) is a plasma membrane-bound hydrolase that converts oleamide to oleic acid. This hydrolase also converts the cannabinoid anandamide, the endogenous ligand for the CB1 cannabinoid receptor, to arachidonic acid, suggesting a role in fatty-acid amide in-activation. Mice lacking FAAH1 have significantly higher levels of anandamide in the brain and show decreased sensitivity to pain, further indicating a role for FAAH1 in the regulation of endocannabinoid signaling in vivo. FAAH1 null mice also demonstrate an increased preference for alcohol and an increased voluntary uptake of alcohol as compared to wild-type mice, indicating a role of FAAH1 in modulating addictive behaviors.