A reverse-phase suspension polymerization process for the manufacture of polymer beads comprises forming aqueous monomer beads of an aqueous solution comprising water-soluble ethylenically unsaturated monomer or monomer blend and polymerizing the monomer or monomer blend to form polymer beads while suspended in a non-aqueous liquid, recovering polymer beads, and then cleaning the non-aqueous liquid. The process comprises providing the non-aqueous liquid in a vessel (1), forming a suspension of monomer beads from the aqueous monomer or monomer blend in the non-aqueous liquid, initiating polymerization to form polymerizing beads, removing a suspension of the polymer beads in non-aqueous liquid from the vessel and recovering, water soluble or water swellable polymer beads from the suspension, in which the non-aqueous liquid contains impurities which comprise particles, and then transferring the non-aqueous liquid from the suspension to a cleaning stage, in which the cleaning stage provides a cleaned non-aqueous liquid suitable for use in a reverse-phase suspension polymerisation process, which cleaning stage comprises removing particles from the non-aqueous liquid in at least one filtration step. The invention also relates to the apparatus suitable for carrying out a reverse-phase suspension polymerisation and polymer beads obtainable by the process or employing the apparatus. The invention further relates to a cleaned non-aqueous liquid obtainable by the process.