Tumour necrosis factor alpha (TNF alpha) is increased in patients with cardiac cachexia, a condition associated with reduced peripheral blood flow both at rest and after interventions causing vasodilation.By contrast, in patients with chronic heart failure (CHF), higher TNF levels are associated with a greater capacity for vasodilation in the arm. To clarify the relationship between peripheral blood flow and TNF in CHF, we studied the relation between TNF alpha and blood flow in the leg (plethysmography, post maximal exercise and 5 min ischaemia) in 34 patients (age 63 +/- 2 years, ejection fraction 29 +/- 3%, peak VO2 16.6 +/- 1.1 ml/kg/min, mean +/- SEM). Peak leg blood flow correlated significantly with total TNF alpha (r = -0.68, p < 0.0001), peak VO2 (r = 0.54), and soluble TNF receptors 1 (r = -0.56) and 2 (r = -0.52, all p < 0.002). TNF alpha, soluble TNF receptors 1 and 2 and aldosterone correlated with peak blood flow independently of age, ejection fraction, peak VO2 and functional NYHA class. TNF alpha was the only parameter that showed strong correlations for peak blood flow in all clinically relevant subgroups (severe vs. mild, ischaemic vs. dilated, cachectic vs. non-cachectic patients). This study shows a close and inverse relationship between peak leg blood flow and the plasma concentration of TNF alpha, suggesting a pathophysiological role for TNF alpha in reducing peak peripheral blood flow in CHF.