Four patients who underwent heart transplantation, in whom coronary obstruction was seen early after transplantation, are described. Repeated acute rejection episodes were detected within the first 2 months in each patient. Coronary obstruction or ischemia was shown through a combination of T1-201 isotopic study findings, evidence of vasculitis of a small coronary arteriole seen at endomyocardial biopsy, or coronary angiographic results. Vigorous treatment for rejection (antithymocyte globulin and bolus methylprednisolone) was given, and coronary artery lesions or myocardial ischemia resolved after treatment. Rejection-induced coronary obstruction should be considered in patients with repeated acute rejection episodes who are predisposed to the development of vascular rejection. Early after transplantation such obstruction is caused by diffuse vasculitis of small and medium-sized vessels and may be reversed with increased immunosuppression.