This paper presents the results of a study on the ¹³⁷Cs content in liver, kidneys and biceps muscles of red deer (Ceravus elaphus) obtained in Warmia and Mazury in 2000/2001. 93 samples from 51 red deer shot in the communes of Reszel, Lelkowo, Olecko, Kętrzyn, Pisz, Ruciane Nida, Ryn, Szczytno, Orzysz, Rozogi, and Olsztynek were analyzed. Concentrations of radiocesium in several samples of muscle tissue of red deer obtained from the European part of Russia was determined for reference. In Warmia and Mazury the average concentrations of ¹³⁷Cs were 20.48 Bq/kg in muscle, 13.26 Bq/kg in liver, and 18.74 Bq/kg in kidneys. As such, these were very low figures. It was only in a few samples of red deer tissues obtained at two locations (Olsztynek, Zaporowo) that the levels of this radionuclide were elevated compared to those from other sites. The least radioactive were samples collected from carcasses of calves, in contrast to those taken from bucks, which contained the highest levels of radiocesium. A wide range of differences in the determinations was obtained. For example, concentrations of radiocesium in muscle tissues varied from 1.91 to 28.55 Bq/kg for calves, 0.91 to 79.20 for does and 2.69 to 137.20 Bq/kg for bulls. The ¹³⁷Cs levels in red deer’s potential foodstuffs also varied from region to region, although it was to a certain extent positively correlated with the amounts of radiocesium determined in the red deer carcasses obtained in these areas.