Interleukin-12 (IL-12) is an important cytokine for maintenance of normal systemic defense and bioregulation. The Japanese herbal medicine Sho-saiko-to (TJ-9) has been administered to 1.5 million Japanese patients with chronic liver diseases. TJ-9 is known to significantly suppress cancer development in the liver and has macrobiotic effects. In the present study, we examined the in vitro production of IL-12 by circulating mononuclear cells from liver cirrhosis patients and the effects of TJ-9 on IL-12 production. The monocyte/macrophage fraction and the lymphocyte fraction of peripheral blood were obtained from 11 HCV-positive liver cirrhosis patients and 12 healthy subjects. Interleukin-12 levels in the supernatants were measured using ELISA kits. The levels of IL-12 produced by the patients' fractions were significantly lower than those produced by healthy subjects (p < 0.01, p < 0.05). However, when TJ-9 was added to the cultures, the IL-12 production levels in both cell fractions increased approximately three fold, and the levels from the monocyte/macrophage fraction were almost the same as those from healthy subjects. This effect of TJ-9 was attributable to two of its seven herb components, that is, scutellaria root and glycyrrhiza root. One possible mechanism for the macrobiotic effects of TJ-9 on liver cirrhosis patients may be the improvement in IL-12 production.