Novel irreversible ligands specific for "peripheral" type benzodiazepine receptors: (+/-)-, (+)-, and (-)-1-(2-chlorophenyl)-N-(1-methylpropyl)-N- (2-isothiocyanatoethyl)-3-isoquinolinecarboxamide and 1-(2-isothiocyanatoethyl)-7-chloro-1,3-dihydro-5-(4-chlorophenyl )-2H-1,4-benzodiazepin-2-one.