Endothelium-dependent vasodilation in the peripheral circulation may be impaired in heart transplant recipients (HTx rec). Conflicting results have been obtained and the mechanisms involved have not been examined. In the present study, we examined whether long-time survivors of heart transplantation (Tx) show signs of endothelial dysfunction in the peripheral microcirculation, and further investigated the possible role of endothelium-related markers and proinflammatory cytokines in this process. The vasodilatory responses to acetylcholine (Ach) (endothelium-dependent) and sodium nitroprusside (SNP) (endothelium-independent) were evaluated by skin laser-Doppler perfusion measurements in 63 clinically stable HTx rec 6 yr (range 1-13 yr) after Tx, and compared with 20 healthy controls. Ten HTx rec were also followed prospectively with three repeated measurements during the first year after Tx. Plasma von Willebrand factor, big-endothelin (b-ET), and proinflammatory cytokines were measured by enzyme immunoassays. Vascular responses to both Ach and SNP were significantly attenuated in the HTx rec compared with controls. In longitudinal testing, there was a significant reduction in endothelium-dependent vasodilation, but not independent vasodilation from 1 to 12 months after Tx. Plasma levels of vWF and b-ET, as well as levels of proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-1beta, were all markedly increased in HTx rec. HTx rec responses to Ach were negatively correlated to TNF-alpha levels in plasma (r = -0.39, p < 0.01). Moreover, there was also a significant positive correlation between plasma b-ET and TNF-alpha (r = 0.34, p < 0.01). In the long-term follow-up of HTx rec, endothelial dysfunction is demonstrated by both regulation of blood flow in the skin microcirculation and by raised markers of endothelial activation in plasma. This endothelial dysfunction may be related to enhanced levels of proinflammatory cytokines in these patients.