Research into the endocannabinoid 'system' has grown exponentially in recent years, with the discovery of cannabinoid receptors and their endogenous ligands, such as anandamide and 2-arachidonoylglycerol (2-AG). Important advances have been made in our understanding of endocannabinoid transduction mechanisms, their metabolic pathways, and of the biological processes in which they are implicated. A decade of endocannabinoid studies has promoted new insights into neural regulation and mammalian physiology that are as revolutionary as those arising from the discovery of the endogenous opioid peptides in the 1970s. Thus, endocannabinoids have been found to act as retrograde signals: released by postsynaptic neurons, they bind to presynaptic heteroceptors to modulate the release of inhibitory and excitatory neurotransmitters through multiple G-protein-coupled receptor (GPCR)-linked effector mechanisms. The metabolic pathways of anandamide and 2-AG have now been been characterised in great detail, and we can anticipate that these pathways -- together with endocannabinoid uptake mechanisms -- will complement cannabinoid receptors as targets for the pharmacological analysis of the physiological functions of these substances. Specific insights into the potential role of endocannabinoid-CB1 receptor systems in central appetite control, peripheral metabolism and body weight regulation herald the clinical application of CB1 receptor antagonists in the management of obesity and its associated disorders.