Abstract: A process is described for the preparation of pyrimidine derivatives having therapeutic properties. They have the general formula: ##SPC1##Wherein A represents an alkylene or alkenylene grouping which together with the carbon atoms of the pyrimidine nucleus to which it is attached forms a homocyclic ring containing five to seven carbon atoms, which homocyclic ring may carry one or more halogen, lower alkyl and/or lower alkoxy substituents and R represents an amino, lower alkylamino or di(lower)alkylamino group, or a nitrogen-, oxygen- or sulphur-containing saturated or unsaturated mononuclear heterocyclic group linked to the pyrimidine ring either through a carbon atom or, when the group contains a nitrogen atom, either through the nitrogen atom or a carbon atom and are prepared by reacting a cycloaliphatic(A)oaminonitrile with a nitrile of the formula R-CN where A and R have the above meanings in the presence of a basic alkali metal-containing compound and then reacting the resultant intermediate with water.