1. The in vitro thoracic aorta, precontracted with norepinephrine, KCl or PGF2 alpha of hypercholesterolemic Pittsburg-Yoshida (YOS) and normolipidemic Brown-Norway (BN) rats of two age groups (2 and 18 months), was relaxed by the calcium antagonists verapamil and nifedipine without any difference between age-matched YOS and BN rats. 2. The relaxant activity of verapamil was impaired in aged rats of both strains and with the different contractile agents. Conversely, no variation with aging of the nifedipine relaxing effect was observed on KCl-induced contraction was the nifedipine relaxant effect differently affected by age, both in YOS and BN rats. 3. In conclusion, prolonged exposure to hypercholesterolemia in YOS rat does not affect aortic response to nifedipine and verapamil. Only the aging process was able to affect vascular relaxation to calcium antagonists.