This paper presents results of one-year monitoring of bioaerosol dispersion from a full-scale sludge composting facility in the east coast of the USA. By using two-stage Andersen air samplers with a sequential sampling procedure developed in this study, a total of 24 sets of bioaerosol samples were collected on petri dishes for plate counting. The sampling program utilized a computer air dispersion model (ISCST) to predict the downwind distance at the maximum concentration. Field samplings were performed at upwind, onsite, and predicted downwind locations. The results of this study conclude that the 95% confidence intervals estimated for the background concentrations were: 75-173 cfu/m3 for aerobic bacteria, 262-706 cfu/m3 for mesophilic fungi, 5.0-14 cfu/m3 for thermophilic fungi, and 2.3-12 cfu/m3 for Aspergillus fumigatus. The maximum probably downwind concentrations were evidently increased for aerobic bacteria and thermophilic fungi, but not for mesophilic fungi, fecal coliform, and fecal streptococcus. The zone of influence was estimated to be in the range of 1500-1800 m from the composting facility. Particles smaller than 8 μm constituted 40% of aerobic bacteria and 70-75% of fungi, which may be inhaled into the lung and cause the hypersensitive effect in the respiration system.