Neurotensin (NT) is a brain and gastrointestinal peptide that fulfills a dual function of neurotransmitter or neuromodulator in the nervous system and of local hormone in the periphery. NT is a neuromodulator of dopamine transmission and of anterior pituitary hormone secretion, and exerts potent hypothermic and analgesic effects in the brain. In the periphery, NT is a paracrine and endocrine modulator of the digestive tract and of the cardiovascular system of mammals and acts as a growth factor on a variety of normal or cancer cells. NT plays many central and peripheral functions through its interaction with specific receptors. Three subtypes of neurotensin receptors, NTSR1, NTSR2 and NTSR3, have been cloned so far. Among them, NTSR1 and NTSR2 belong to the family of G protein-coupled receptors and mediate the most known functions of NT, whereas the third neurotensin receptor’s function remains to be established.