The invention provides a process for producing an olefin polymerization catalyst, comprising an organometallic compound of a transition metal or of an actinide or lanthanide, in the form of solid catalyst particles, comprising forming a liquid/liquid emulsion system which comprises a solution of one or more catalyst components dispersed in a solvent immiscible therewith; and solidifying said dispersed phase to convert said droplets to solid particles comprising the catalyst and optionally recovering said particles.