605264 Disclosed herein is the delta crystalline form of perindopril L-arginine salt of formula (I) characterised by the following X-ray powder diffraction peaks measured using a diffractometer with a copper anticathode and expressed in terms of Bragg’s angle 2 theta: 4.3, 11.0, 11.1, 11.9, 10 12.5, 13.2, 14.6, 16.0, 19.2, 19.4, 20.0, 21.9, 22.2 and 22.6； processes for the preparation thereof； and a pharmaceutical composition for use in the treatment of cardiovascular diseases such as arterial hypertension, heart failure or stable coronary disease. Wherein the process for the preparation of the delta crystallisation form comprises crystallisation or recrystallisation from a binary mixture of acetonitrile, ethyl acetate or methyl tert-butyl ether and dimethyl sulphoxide or a ternary mixture of acetonitrile, dimethyl sulphoxide and toluene, at a temperature higher than 20°C. Particularly, wherein the binary mixture of acetonitrile, ethyl acetate or methyl tert-butyl ether and dimethyl sulphoxide has a ratio of acetonitrile/dimethyl sulphoxide, ethyl acetate/dimethyl sulphoxide or methyl tert-butyl ether/dimethyl sulphoxide ranging from 90/10 w/w to 10/90 w/w； the temperature of the medium is between 25 and 80°C, inclusive； and the mixture is heated to a temperature of from 60 to 80°C.
