Background Numerous phenolic compounds are consumed in the diet in a range of foods. There are very few studies of the effects of these compounds on the production of lymphocyte-derived cytokines. Aim of the study To investigate the effects of five phenolic compounds on cytokine production by cultured human lymphocytes. Methods Human whole blood cultures were stimulated with the T cell stimulant concanavalin A for 48 h in the presence of phenolic compounds (vanillic acid, syringic acid, kaempferol, oleuropein and tyrosol) at concentrations up to 10−4 M. Interleukin (IL)-2, IL-4 and interferon-γ (IFN-γ) concentrations were measured in the culture supernatants by ELISA. Results IFN-γ concentration was significantly lower in cultures containing 10−4 M kaempferol than in cultures with kaempferol at 10−7, 10−6and 10−5 M or without kaempferol. The other phenolic compounds did not affect IFN-γ concentration and none of the phenolics tested affected IL-2 or IL-4 concentrations. Conclusions Some, but not all, phenolic compounds can decrease IFN-γ production by stimulated human whole blood cultures.