Circulating levels of the proinflammatory cytokines interleukin-6 (IL-6), IL-8, and tumor necrosis factor-alpha (TNF-alpha) were measured in 13 children with autoimmune hepatitis (AIH) (seven with type 1 and six with type 2). In untreated children with type 1 AIH, TNF-alpha, IL-6, and IL-8 levels were elevated when compared to those of healthy controls (p < 0.005, p < 0.02, p = 0.06, respectively), whereas in children with type 2 AIH, cytokine levels were normal in all except one sample. A significant decrease in circulating IL-6, IL-8, and TNF-alpha was observed when patients were evaluated during a subsequent remission. We found no significant correlation of cytokine levels with alanine aminotransferase (ALT) activity, total serum gamma-globulins, or prothrombin activity. In patients with cirrhosis, serum IL-8 and IL-6 levels were higher (significantly in the case of IL-8) than those of patients without cirrhosis. In conclusion, activation of the in vivo production of the proinflammatory cytokines IL-6, IL-8, and TNF-alpha appears to be associated with type 1 but not with type 2 AIH.