Polyvinylacetophenone was made by the Friedel‐Crafts reaction of acetyl chloride or acetyl bromide on polystyrene, in carbon disulfide, using aluminum chloride. Similar reactions, using bromoacetyl bromide or chloroacetyl chloride, gave insoluble polyvinylphenacyl halides. A soluble, low‐molecular‐weight polyvinylphenacyl chloride was obtained using chloroacetyl chloride and monomeric styrene. Polyvinylphenacyl bromides of limited Solubility were obtained by direct bromination of polyvinylacetophenone. Vacuum pyrolysis of polyvinylacetophenone gave p‐vinylacetophenone monomer in good yield. At atmospheric pressure, the product was about half p‐vinylacetophenone and half p‐ethylacetophenone. At intermediate pressure, an intermediate proportion was obtained.