Abstract. In some regions of Germany radiocaesium contamination of wild boar (Sus scrofa) is either staying fairly constant or slightly increasing on average, concurrently exhibiting an extraordinary variability. The reasons for this peculiar contamination pattern were investigated from 2002 to 2004 in an area located in the Bavarian forest. The microscopic analyses of 70 stomachs gave detailed information on the food composition. Potential food items sampled in the investigation area were measured for their radiocaesium level. Deer truffles (Elaphomyces granulatus), a preferred delicacy of wild boar, turned out to play a key role. This fungus showed contamination levels exceeding those of edible mushrooms and other food components by an order of magnitude and more. Despite their low weight proportion of about 6% of the stomach content on average, more than three quarters of the radiocaesium uptake can be ascribed to deer truffles. Their irregular consumption and the dynamics of radiocaesium in forest soil explain the peculiar contamination pattern of wild boar. Predictive modelling of radiocaesium contamination of wild boar should always take into account deer truffles, especially their occurrence, contamination levels and irregular consumption.