Sclerotinia sclerotiorum is an emerging fungal pathogen affecting soybeans in the United States. In response to its emergence, exposures to particulates, bioaerosols, endotoxins, S. sclerotiorum, and b(1-3)-glucans were characterized during soybean harvesting. Air sampling was performed on soybean harvesters (combines) and on the farmers in closed cabs as personal samples during harvesting at 17 farms in 1997 and repeated at 15 in 1998. S. sclerotiorum infestation was evident in the fields at 8 of the sites (44%). The geometric mean concentrations (and geometric standard deviations) measured on the combines in 1998 were as follows: total dust, 11.9 (2.8) mg/m3; inhalable dust 11.7 (6.4) mg/m3; and b(1-3)-glucans, 5027 (7) ng/m3. Values for the personal samples in 1998 were as follows: total dust, 1.2 (6.7) mg/m3; inhalable dust, 1.1 (5.3); and b(1-3)-glucans, 674 (9) ng/m3. These concentrations were two- to threefold higher than in the previous year. Ambient endotoxin concentrations were 4438 EU/m3 in Year I and 459 EU/m3 in Year II. Particle size distribution measurements on the combines yielded mass median aerodynamic diameters of 6.6 mm on the combine and 4.0 mm inside the combine cab. Closed combine cabs provided an average workplace protection factor of 11.7 for total dust. Nevertheless, personal exposures to organisms inside combine cabins ranged from 3.63104 to 4.03108 organisms/m3. These data indicate the potential exists for high exposures to organic dust and bioaerosols during soybean harvesting.