PURPOSE: To produce an internally sized paper superior in a sizing effect, an yield and a fiber dispersibility by adding a cationic retention aid to a cellulosic suspension, treating it under specified conditions to obtain a suspension of coagulates, draining it to form a sheet and drying it.

CONSTITUTION: Preferably 0.01-0.3% (based on a dry weight of cellulose) of a water soluble, cationic retention aid such as cationic starch is added to a cellulosic suspension to form flocs. They are broken without substantial resuspension of fibers down to cationically charged microflocs. A nonionic or anionic size emulsion is added to the suspension after flocculation, and a soln. or dispersion of an anionic compd. selected from org. polymer substances, bentonite and colloidal silicates is added, to obtain a suspension of coagulates contg. the size. Further, the suspension of coagulates is drained to form a sheet, which is dried, to obtain the objective internally sized paper.