Polyurethanes are recycled by comminution to particle sizes of from 0.01 to 2 mm and addition to the polyaddition mixture for preparing polyurethanes from(a) polyisocyanates,(b) substances reactive toward isocyanates and having active hydrogens, and, if desired,(c) chain extenders and/or crosslinkers, catalysts, blowing agents and customary additivesin an amount of from 0.1 to 40% by weight, based on the poly-addition mixture.