Abstract: The invention describes a process for the preparation of a particulate polymer, said process comprising: i) forming an aqueous dispersion comprising a particulate polymer seed material and a first organic compound; ii) allowing said first organic compound to diffuse into said seed material to produce a pre-swollen seed material; iii) contacting said pre-swollen seed material in aqueous dispersion with said first organic compound and a second organic compound, preferably one which is soluble in said first organic compound; iv) allowing or causing said first and second organic compounds to pass into said pre-swollen seed material to produce an activated seed material; v) contacting said activated seed material with a monomer and effecting suspension polymerization thereof.