Abstract: Process for the manufacture of polyurethane adhesives with uniform molecular weights which are accurately adjustable and reproducible consisting of diisocyanates, polyols, chain extenders if required, catalysts and additives, all of which are soluble in polar, organic solvents which are inert with respect to isocyanate groups. The polyaddition process is carried out by using an excess of diisocyanate, the reaction is terminated upon reaching the desired molecular weight, and the still existing excess isocyanate groups are allowed to react with alcohols, ammonia and/or amines. The process is characterized in that the polyurethanepolyaddition products are crushed into particles of 1-15 mm and that they are treated with possibly substituted primary, aliphatic mono- to trivalent alcohols, ammonia and/or aliphatic, cycloaliphatic or aromatic mono- or diamines in the liquid or vapor phase in the absence of organic solvents.