The aim of the study was to assess whether immunomodulating effects produced by ochratoxin A (OTA) may influence the course of an experimental infection of pigs with Salmonella Typhimurium 27 Nat (STM 27 Nair). 8-week old pigs were administered 50 g OTA per kg body weight per day via feed. Either 7 or 14 days after beginning of OTA application, these pigs and untreated controls were challenged orally with STM 27 Nair. Different systemic immune parameters in blood and OT A concentration in serum and organs were examined. The number of STM 27 Nair was detected in faecal samples of the pigs. Despite high concentrations of OTA in sera and organs, systemic immune parameters were not modified compared with controls. Significant changes in these parameters were induced only by the Salmonella infection. Pigs pretreated with OTA excreted STM 27 Nair in slightly higher (not significant) concentrations than untreated controls. As the immunomodul ating effects produced by OT A after oral administration seem to be considerably lower than the effects induced by a challenge with Salmonella Typhimurium in a high dose, experiments using reduced doses for infection should give further information on the effect on Salmonella shedding.