Abstract: Amidines derived from 3-aminoethyl indoles of formula (I) ##STR1## where R.sub.1 is an atom of hydrogen or a lower alkyl or alkenyl group: R.sub.2 is an atom of hydrogen or a lower alkyl or alkenyl , aryl, arylalkyl or cycloalkyl group; R.sub.3 and R.sub.4 may be the same or different and are an atom of hydrogen or a lower straight or branched chain alkyl group; and R.sub.5 is an atom of hydrogen; a straight or branched chain alkyl, alkenyl or alkynyl group, which may be substituted with an hydroxy group, alkoxy, alkoxycarbonyl, carboxyl, trifluoromethyl, halogen, carbonyl, cyano; a cyano group, phenyl, aryl, cycloalkyl, heterocycle or arylalkyl, optionally substituted with a hydroxy, alkoxy, halogen, amino, alkoxycarbonyl, carboxyl, trifluoromethyl, carbonyl, cyano, nitro, lower alkyl, lower alkenyl, or may form an optionally substituted heterocycle with R.sub.4 and with the nitrogen atom; and the physiologically acceptable salts thereof.