['Coronary endothelial dysfunction may be an early marker for cardiac allograft vasculopathy (CAV) in orthotopic heart transplant recipients. We used serial studies to evaluate changes in coronary endothelial function in patients with and without clinically evident CAV.', 'In serial studies with intravascular ultrasound (IVUS) and Doppler flow wire measurements, we previously demonstrated that annual decrements in coronary endothelial function are associated with progressive intimal thickening.', 'We studied 45 patients annually, beginning at transplantation until pre-specified end-points (angiographic CAV or cardiac death) were reached. At each study, we measured coronary endothelial function using intracoronary infusions of adenosine, acetylcholine, and nitroglycerin. We simultaneously recorded IVUS images and Doppler velocities.', 'Of the 45 patients studied, 9 reached end-points during the study (6 had CAV and 3 died). The mean annual change in area response to acetylcholine was -4.5% +/- 3.0% in patients who reached end-points and -0.9% +/- 1.5% in those who did not (p = 0.04). The mean annual decrement in flow response to acetylcholine was greater in patients who reached end-points (-31% +/- 11% vs -5% +/- 5%, p = 0.08). Responses to adenosine and nitroglycerin did not differ.'] Do changes in coronary endothelial function predict progression of allograft vasculopathy after heart transplantation?