Occupational, biological factors of microbial, plant and animal origin may become a health hazard to the exposed workers. The aim of the study was to assess the knowledge of biological agents present in the work environment, related health risks, and health protection against biological exposure at work among workers of certain occupational categories.A population of 150 workers, employed in the health, forestry and municipal services, was interviewed using a specially developed questionnaire. Each occupational category comprised 50 workers.The level of workers' knowledge of occupational, biological agents, their effect on human body, symptoms and diseases induced by occupational exposure to biological hazards is rather limited in the study groups. Personal protective measures, prophylactic vaccination and compliance with principles of personal hygiene are considered to be the most effective ways of health protection against occupational exposure to biological hazards.