The aim of the study was to find the sources of 137 Cs in wild boar food in the natural ecosystem. The main emphasis is focused on the analyses of wild boar muscles and the content of wild boar stomach. Boars weighing 20 to 100 kg were killed at two locations. The highest specific activities of muscles were measured in boars originated from the Dvorce location; the average specific activity in boars killed on 14 Cs specific activities higher than that of the detection limit. Consequently, underground mushrooms probably represent the main source of radiocesium in the food chain of boars. A remarkable reduction of 137 Cs specific activities in boar muscles is not expected at the post-Chernobyl radiocesium contaminated locations with the occurrence of Elaphomyces granulatus within next two decades.