Background Congestive heart failure (CHF) and heart transplantation (HTX) are characterized by endothelial dysfunction as indicated by elevation of markers of endothelial function, including endothelin and von Willebrand factor (vWF). However, previous studies included both patients with idiopathic dilated cardiomyopathy and ischemic heart disease; the latter condition shows endothelial dysfunction, per se. The 2 endothelial factors have different origin and may provide different information about endothelial dysfunction in CHF and after HTX caused by idiopathic dilated cardiomyopathy. Methods We investigated plasma endothelin and vWF, the relation between these 2 factors, and determinants of endothelin and vWF plasma levels in 32 healthy controls, 25 patients with CHF, and 22 patients who had HTX; both conditions were caused by idiopathic dilated cardiomyopathy. Results Plasma endothelin was elevated in CHF (6.8 ± 3.4 pg/mL) and after HTX (6.1 ± 2.1) compared with healthy controls (4.0 ± 1.0, P < .0001 for both). VWF was also elevated in CHF (1.6 ± 0.6 U/mL) and after HTX (2.6 ± 1.0) compared with healthy controls (1.0 ± 0.5, P < .0001 for both). VWF was increased after HTX compared with CHF (P < .001), in contrast to similar endothelin levels in CHF and after HTX. Plasma endothelin and vWF correlated in both CHF (r = 0.65, P < .001) and HTX (r = 0.66, P < .001) but not in controls. In CHF, New York Heart Association functional class was an independent determinant of vWF (P < .0001) and furosemide dose of endothelin (P < .0001). In cardiac transplant recipients, plasma albumin was an independent determinant of vWF (P < .01), and plasma sodium and furosemide dose were independent determinants of endothelin (P < .01). Conclusions Plasma endothelin and vWF were directly correlated in both CHF and after HTX caused by idiopathic dilated cardiomyopathy. However, the production of the 2 factors appeared to be stimulated by different mechanisms and provided different information about endothelial function, as indicated by the different determinants and different response to heart transplantation. (Am Heart J 1999;137:549-54.)