Beta crystalline form of perindopril arginine salt (I), characterized by the X-ray diffraction diagram on powder, measured by a diffractometer (copper anticathode) and exhibited a Bragg angle 2 theta (expressed in percentage in relation to the most intense line), an interreticular distance (d), an intensity and a relative intensity, as given in table of the specification, is new. Beta crystalline form of perindopril arginine salt of formula (I), characterized by the X-ray diffraction diagram on powder, measured by a diffractometer (copper anticathode) and exhibited a Bragg angle 2 theta (expressed in percentage in relation to the most intense line), an interreticular distance (d), an intensity and a relative intensity, as given in table of the specification, is new. Independent claims are included for: (1) a composition comprising (I) in combination with inert and nontoxic vehicles； and (2) the preparation of (I). ACTIVITY : Cardiovascular-Gen； Hypotensive； Cardiant. MECHANISM OF ACTION : Angiotensin I converting enzyme inhibitor. No biological data given.
