Interleukin 6 (IL-6) is a pleiotropic cytokine which possesses a broad spectrum of action in diverse pathological conditions. It is mainly produced and metabolised in the liver where it carries out one of its best known actions in the mediation of the acute phase response. We studied its behaviour in hepatocellular carcinoma to evaluate its clinical prognostic role. We determined serum IL-6 concentrations in 39 patients with hepatocarcinoma (27 males and 12 females) and 25 healthy controls (15 males and ten females). Our results showed a significant increase in serum IL-6 concentrations in hepatocarcinoma subjects compared with controls (P < 0.005) and an elevated positive correlation (r = 0.616) between IL-6 and size of the hepatocarcinoma. Our study demonstrated that IL-6 is able to influence hepatocarcinoma progression by acting as an autocrine tumoral growth factor and depleting immune surveillance.