The in vitro effects of four Fusarium toxins, fumonisin B(1) (FB(1)), alpha-zearalenol (alpha-ZEA), nivalenol (NIV) and deoxynivalenol (DON), on mitogen-induced cell proliferation were determined in swine whole-blood cultures. Considering the lack of sufficient toxicological data both on single and in combination effects, in vitro studies may contribute to risk assessment of these toxins. Incubation with increasing concentrations of FB(1) did not produce any consequence on proliferation; in contrast alpha-ZEA, NIV and DON showed an inhibitory effect. Dose-response curves for each mycotoxin were generated. NIV was found to be the most potent toxin followed by DON and alpha-ZEA. The effects of both FB(1)+alpha-ZEA and NIV+DON mixtures were also analysed to investigate possible interactions. The results indicated that combination of FB(1)+alpha-ZEA produces a synergistic inhibition of porcine cell proliferation; whereas there is no interaction between DON and NIV on porcine whole-blood proliferation, at tested concentrations.