Process for preparing an olefin polymerisation catalyst component in the form of particles having a predetermined size range, said process comprising the steps of a) preparing a solution of a complex of a Group 2 metal and an electron donor by reacting a compound of said metal with said electron donor or a precursor thereof in an organic liquid reaction medium; b) adding said solution of said complex to at least one compound of a transition material to produce an emulsion, the dispersed phase of which contains more than 50 mol % of the Group 2 metal in said complex; c) agitating the emulsion, optionally in the presence of an emulsion stabilizer, in order to maintain the droplets of said dispersed phase within the average size range 5 to 200 m; d) solidifying said droplets of the dispersed phase; and e) recovering the solidified particles of the olefin polymerisation catalyst component, wherein a turbulence minimizing agent (TMA) is added to the reaction mixture before solidifying said droplets of the dispersed phase, said TAM being inert and soluble in the reaction mixture under the reaction conditions.