Abstract: Amidine derivatives of opioids of the formula YN—X—(NH)n-C(?NR)—R? in which YN is a morphine-like opioid radical; X is a direct bond, a substituted or unsubstituted, branched, straight-chained or cyclic alkylene having from 1 to 6 carbon atoms, optionally containing one or two heteroatoms in the alkyl chain, or an optionally substituted, branched or straight-chained alkenylene having from 4 to 10 carbon atoms; R and R? are independently hydrogen, alkyl, substituted alkyl, alkene, substituted alkene, alkyne, substituted alkyne, aryl, substituted aryl, heterocycle, substituted hetercycle or cyano; and n is 0 when X is said direct bond, or n is 1 when X is said alkylene or alkenylene. The compounds are effective in treating pain, and have effect in the peripheral nervous system, with comparably less or no activity in the central nervous system.