In 18 patients with chronic active hepatitis C, we determined the Montgomery and Asberg Rating Scale (MADRS), the Hamilton Anxiety Rating Scale (HAM-A), serum DPP IV activity, the kynurenine/tryptophan (K/T) quotient, which is an indicator of cytokine (in particular IFN)-induced catabolism of tryptophan, and serum interleukin-8 (IL-8) before starting therapy and 2, 4, 16 and 24 weeks after immunotherapy with IFN alpha.