AIMS To clarify whether the lower interferon gamma (IFNγ) production by lymphocytes in patients with liver diseases is due to defects of lymphocytes themselves or of other cofactors such as interleukin-2(IL-2). METHODS Peripheral blood mononuclear cells (PBMCs) from patients with various liver diseases were cultured with or without PHA and IL-2. The cells were harvested and counted and the su- pernatants were tested for IFNγ by a sensitive and quantitative ABC-ELISA. RESULTS IFNγ was not round in serum samples from patients as well as normal individuals. However,in supernatants of non-in- duced and induced PBMCs,IFN7 was detected by ABC-ELISA. In non-induced PBMCs (group 1),the content of IFNγ in super- natants from control,CAH,CPH and HCC was 8.72 μg/L, 5.03 μg/L,6.02 μg/L and 4.91 μg/L respectively. The pro- duction of IFNγ in liver disease was significantly decreased,com- pared to control. In group 2 in which PBMCs were stimulated with PHA,the content of IFNγ was 22.71,17.12,14.54 and 17.63 μg/L respectively. In group 3 in which PBMCs were in- duced by IL-2,the amount of IFN7 in supernatant from control (60.67 μg/L) was much larger than those from CAH (21.70 μg/ L),CPH (24.00 μg/L) and HCC (19.15 μg/L) (P<0.01). Comparing the amount of IFNγ in group 3 (IL-2-induced) with that in group 1 (non-induced),we found that IFNγ production was en- hanced by nearly 4 folds in liver diseases and by over 7 folds in control,Whereas the number of PBMCs,whether from liver dis- eases or from control,was increased by only approximately 3 folds. CONCLUSIONS The decreased production of IFNγ in liver dis- eases including HCC is mainly due to endogenous defects of lym- phocytes though the defects of stimulating cofactors such as IL-2 may also be involved.