Accelerated coronary arteriosclerosis remains a major problem for the long-term survival of cardiac transplant recipients. However, the pathogenesis of graft vasculopathy is poorly understood and there is no effective therapy. Tranilast is a promising drug that may prevent post-angioplasty restenosis. Here, we investigated whether orally administered tranilast inhibits the development of intima hyperplasia in a mouse model of cardiac transplantation. Cardiac allografts from BALB/c mice were transplanted heterotopically into C3H/He mice. Mice were administered either vehicle or tranilast everyday by gavage. Morphometrical analysis of the cardiac allografts harvested at 2 months revealed that the administration of tranilast significantly reduced the development of coronary atherosclerosis. In the mice treated with tranilast, up-regulation of the cyclin-dependent kinase inhibitor p21 was observed in the allografts, accompanied by a reduced number of proliferating cells. Tranilast also suppressed transforming growth factor-beta (TGF-beta) expression. Tranilast may be effective in preventing transplant-associated arteriosclerosis through its anti-inflammatory and anti-proliferative effects.