Paper is made by providing an anionic aqueous emulsion of a size, usually a reactive anhydride size, and mixing it into a cellulosic suspension prior to drainage of the suspension to form a sheet which is then dried to provide paper (including paper board). The emulsion is preferably stabilised wholly or mainly by 0.5 to 30 parts by weight (per part by weight size) of water soluble, anionic, polymeric stabiliser, which is preferably anionic starch. Alternatively, the emulsion may be added to the cellulosic suspension while it is anionic, before mixing retention into it. The emulsion may be added to the cellulosic suspension after cationic retention aid has been added to it, the emulsion being added with, before or after mixing anionic microparticulate material or other anionic bridging aid, prior to drainage of the suspension.