It is well known that some kinds of immunological functions, s.c. NK activity, IFN or IL-2 production of spleen cells are decreased in mice with protein calorie malnutrition (PCM) compared with those of well-nourished mice. In this study, nutritional conditions of cancer bearers were demonstrated to have serious influence on the effects of immunochemotherapeutic agents as shown herewith. (1) Intra-tumoral 5-FU concentration was lower in PCM mice or starved mice than in mice fed a normal diet. (2) Transplanted mammary tumor, MM-48, was paradoxically grown in PCM mice after 7 days i.p. injection of OK-432 or Lentinan, but the tumor burden was relatively decreased after the same treatment in N-group mice. (4) The life prolongation effect of rIL-2 and OK-432 against ascitic hepatic carcinoma, MH-134, was recognized in C 3H/He mice. On the other hand, there was no observable effect by sequential i.p. injection of PCM mice sera together with rIL-2 and OK-432. (5) Clinically, a randomized study of advanced or recurrent gastric cancer patients treated with MMC and FT(MF) with or without Lentinan was performed. Excellent end-point results were obtained only in Lentinan-administered patients with normal protein levels, but no such effects were noted in patients with low protein levels (below 5.9 g/dl). These findings suggest that the nutritional environment of the cancer bearing host has an important role in the effect of some kinds of BRMs.