Compounds containing the amidine group are manufactured by heating a nitrile of the general formula R.CN (wherein R represents an alkyl, aryl, aralkyl, alicyclic or heterocyclic group, which groups may contain substituents) with a compound of the general formula NHR1R2 (wherein R1 and R2 each represent hydrogen or an alkyl, aralkyl or alicyclic radical) in the presence of a salt of ammonia, a primary, secondary of tertiary alkylamine, aralkylamine or alicyclic amine or a tertiary aryl of heterocyclic -amine. The compound NHR1R2 may be replaced by a compound NR1R2.CO.NH2, which acts as a source thereof under the reaction conditions, whilst the ammonium or amine salt employed may be formed in situ by the reaction of an acid with ammonia or an amine of the stated type or a substance which acts as a source thereof. In examples: (1) benzyl cyanide is heated with ammonium benzenesulphonate while passing in ammonia gas, producing phenylacetamidine benzenesulphonate; (2) p-methylsulphonylbenzonitrile is heated with ammonium methanesulphonate or ammonium chloride while passing in ammonia gas, the the product is treated with ammonium benzenesulphonate solution to form p - methylsulphonylbenzamidine benzenesulphonate; (3) the same product is obtained by treating p-methylsulphonylbenzonitrile as in (1); (4) the ammonium salt in (2) is replaced by ammonium thiocyanate, and the product is isolated as hydrochloride; (5) p-nitrobenzonitrile is treated as in (1) to give p-nitrobenzamidine benzenesulphonate; (6) 3 : 5-dinitrobenzonitrile similarly yields 3 : 5-dinitrobenzamidine benzenesulphonate; (7) p-methylsulphonylbenzonitrile is heated with dimethylamine benzenesulphonate while passing in ammonia gas, yielding the product of (2); (8) p : p1 - dicyano - a : g - diphenoxypropane is treated as in (1) and the product is worked up to give p : p1 - diamidino - a : g - diphenoxypropane dihydrochloride; (9) p-methylsulphonylbenzonitrile is heated with urea and ammonium benzenesulphonate and the product is treated with sodium hydroxide solution to liberate p - methylsulphonylbenzamidine; (10) p-nitrobenzonitrile is heated with urea and benzenesulphonic acid hydrate, and the product is converted, via the free base, into p-nitrobenzamidine picrate; (11) 2 - cyanopyridine is treated as in (9) and the product is converted, via the free base, into 2-amidinopyridine picrate; (12) n-heptyl cyanide is heated with cyclohexylamine and its toluene-p-sulphonate, and the product is converted, via the free base, into N-cyclohexylcaprylamidine hydrochloride; (13) benzyl cyanide is heated with cyclohexylamine and its hydrochloride to form N-cyclohexylphenylacetamidine hydrochloride; (14) the cyclohexylamine hydrochloride in (13) is replaced by ammonium chloride; (15) the cyclohexylamine hydrochloride in (13) is replaced by pyridine benzenesulphonate, and the product is converted, via the free base, into its hydrochloride; (16) p-methylsulphonylbenzonitrile is heated with ammonium benzenesulphonate while passing in dry dimethylamine, and the product is converted, via the free base, into N : N-dimethyl - p - methylsulphonyl benzamidine hydrochloride; (7) p-methylsulphonylbenzonitrile is heated with N : N-dimethylurea and dimethylamine hydrochloride, and the product is converted, via the free base, into N : N-dimethyl - p - methylsulphonylbenzamidine picrate.