Abstract: The invention relates to reduction of polymer buildup during the suspension polymerization of vinyl chloride, either alone or with other olefinically unsaturated monomers copolymerizable therewith. There is employed a particular combination of ingredients in the polymerization recipe, the essential features being the use of a water phase inhibitor and an oil phase inhibitor along with a substantially water-insoluble polymerization initiator and operating at a high pH. A multiplicity of charges may be polymerized in the reactor without opening the same.