New formulations of novel polyurethanes based on cardanol-formaldehyde resins, commercial polypropylene glycols and two different aliphatic diisocyanates are reported. Cardanol based novolac type phenolic resin has been condensed with hexamethylene diisocyanate/ isophorone diisocyanate to produce rigid polyurethanes. Tough polyurethanes have been produced by condensing the commercially available polyols viz., polypropylene glycol-1200(PPG-1200) and polypropylene glycol-2000 (PPG-2000) with the above system. The ageing performance of the newly developed polyurethanes has been studied. These studies revealed better hydrolytic, chemical and environmental resistance of rigid polyurethanes and also the high performance character of the isophorone diisocyanate based polyurethanes with respect to their ageing conditions.