Abstract: A reaction system for forming a thermoset urethane or polyurethane comprising at least one polyol, at least one isocyanate, and a zinc-containing catalyst. In some aspects, the polyol may be a monomeric polyol comprising secondary hydroxyl groups or it may be a polymeric polyol comprising residues of the monomeric polyol. The zinc-containing catalyst may be effective for catalyzing the reaction of the polyol and isocyanate, particularly when at least a portion of the secondary hydroxyl groups in the monomeric or polymeric polyol are hindered secondary hydroxyl groups. Urethanes and polyurethanes formed as described herein may be used in coating compositions, including powder coating compositions, solvent-based coating compositions, and waterborne coating compositions, as well as in many other applications.