In order to investigate the diffusion of infections transmitted by ticks (TBE and Lyme borreliosis) in forest workers, a serological investigation was carried out in the Province of Trento (Northern Italy) on the sera of 465 subjects at potential risk (foresters, hunters, woodcutters, gamekeepers). Antibodies for TBE virus were found in 5 subjects (1.07%) working in the same area, and antibodies for Borrelia burgdorferi were found in 15 subjects (3%). All three clinical cases of TBE identified in the Province of Trento reported that they had been bitten by ticks in the same geographical area. The presence of specific antibodies for TBE virus was tested on the sera of animals grazing in several areas: 4 positive cases were observed in the same area as the human cases reported above.