The role of vitamin B6 as a key component in a number of biological events has been well established. Based on the relationship between chronic inflammation and carcinogenesis on the one hand, and the interaction between immune and cancer cells expressed by modulated cytokine production on the other hand, the aim of the present work was to examine the possibility that vitamin B6 affects cancer development by an interference in the cross-talk between human peripheral blood mononuclear cells (PBMC) and those from two colon carcinoma cell lines. Both non-stimulated PBMC and mononuclear cells induced for cytokine production by HT-29 and RKO cells from human colon carcinoma lines were incubated without and with 4, 20 and 100 μg/ml of pyridoxal hydrochloride (vitamin B6) and secretion of TNF-α, IL-1β, IL-6, IFN-γ, IL-10, and IL-1ra was examined. Vit B6 caused a dose-dependent decrease in production of all cytokines examined, except for that of IL-1ra. The results indicate that vitamin B6 exerts an immunomodulatory effect on human PBMC. The finding that production of inflammatory cytokines is more pronounced when PBMC are in contact with malignant cells and markedly inhibited by the vitamin suggests an additional way by which vitamin B6 may exert its carcinopreventive effect.