To ascertain whether elevated levels of circulating proinflammatory cytokines in patients with advanced heart failure are due to congestive heart failure or due to cachexia or infection complicating heart failure, we measured prospectively plasma concentrations of tumor necrosis factor-α (TNF-α), interleukin-lβ (IL-lβ), interleukin2 (IL-2), and interleukin-6 (IL-6) in 12 patients with mitral stenosis with moderate congestive heart failure, but not with cachexia or infection. Blood samples were obtained from the peripheral vein and right and left atria of the patients during percutaneous mitral valvuloplasty. Levels of TNF-α, IL-lβ, IL-2, and IL-6 in the plasma from the peripheral vein and right and left atria of these patients were not elevated compared with those from the peripheral vein of a control group of 10 normal subjects. On the other hand, plasma levels of TNF-α, but not IL-lβ, IL-2 or IL·6, were elevated in 4 of 9 patients with congestive heart failure complicated with cachexia and/or infection. Our results suggest that proinflammatory cytokine levels are not elevated in congestive heart failure uncomplicated with cachexia or infection.