The paper presents the results of seroepidemiologic studies concerning tick-borne encephalitis (TBE) in 1,583 persons (1,261 forestry workers and 233 farmers) from the Lublin region (eastern Poland) occupationally exposed to ticks and in 130 healthy blood donors (a control group). The mean percentage of seropositive reactions in forestry workers amounted to 19.8% and in farmers 32.0%. Based on 5-year research (1994-1998) conducted in 5 districts of the Lublin region, the existence of endemic foci of TBE was detected in the district of Biała Podlaska, on the areas of Radzyń Podlaski and Parczew, where the percentage of seropositive reactions in forestry workers exceeded 50%. Statistical analysis showed that the frequency of seropositive reactions in forestry workers and farmers was significantly greater compared to control group (p<0.001 and p<0.05, respectively). It indicates that these groups are occupationally exposed to TBE virus. In the years 1994-98, a total of nine clinical cases of TBE (acute neuroinfection) in forestry workers and fourteen clinical cases in farmers were confirmed serologically. The effectiveness of specific immunization against TBE was proved on the basis of 100% seroconversion in 56 earlier seronegative forestry workers. The obtained results proved that forestry workers and farmers in Poland are under increased risk of infection with TBE virus.