Cocaine- and amphetamine-regulated transcript (CART) peptides attracted much attention after the discovery that the level of CART mRNA is increased in rat striatum after acute administration of cocaine and amphetamine. The most widely investigated sequence is CART (55-102), whose roles were confirmed in modulation of various physiological processes such as feeding, energy expenditure, stress control, endocrine secretion, and reward. However, peptides other than (55-102) may be generated from the CART precursor as well. This review describes biological activity of peptides derived from the CART precursor in vivo, and of synthetic CART fragments that have not been found in the nature. In particular, the activity of CART (85-102) is described, whose ability to exert behavioral responses was confirmed by the observed attenuation of the expression of sensitization to morphine-induced hyperlocomotion. This fragment also decreased the number of escape jumps evoked by naloxone in morphine-addicted mice after intracerebroventricular administration.