Working time in conditions of exposure to hazardous factors is an important element indispensable for the evaluation of human exposure in the working environment. Agricultural work is accompanied by co-occurrence of many risk factors threatening farmers' health, e.g. dust, elements of the thermal environment, noise, vibration, chemical and biological agents. Biological factors cause diseases with contagious, allergic or immuno-toxic backgrounds which constitute the majority of farmers' occupational diseases registered in Poland. Exposure to hazardous factors in agricultural working environment is due to contact with plants, animals and organic wastes, more precisely--with microbes, plant and animal particles present in aerogenic agricultural dust, as well as pathogens of contagious and invasive diseases present in contaminated soil, water and plants. Data concerning the duration of farmers' exposure to biological and other factors of the working environment were obtained with the use of the Private Farmer Work Chart. Time-schedule observations concerned an annual work cycle. The study covered 30 farms with the following production profiles: plant (Group A), animal (Group B) and mixed production (Group C). The total working time was: in Group A - from 106-163 % of the legal working time; in Group B - from 75-147 %; in Group C - from 136-167 %. Among 48 work activities contributing to the full working cycle among the farmers examined, 15 activities were accompanied by 5 factors. These were mainly field activities which covered plant harvesting and fertilizing, chemical plant protection, as well as cultivation activities. Agricultural dust and elements of the thermal environment were the environmental factors most frequently accompanying agricultural work, followed by contact with biological factors, noise, vibration, and chemical agents. Biological factors are a specific element associated with 19 work activities, mainly the spreading of manure, animal breeding and plant harvesting. Farmers' working time in conditions of exposure to these factors in the group of plant producers was 51 % of the total working time on average, among animal breeders--80 % and in the case of mixed production--77 %.