Carbohydrate and protein contents of grain dusts were determined, and morphological characteristics were investigated. Airborne dusts of barley, corn, flax, oats, and durum and spring wheat were collected in grain elevators in Minnesota. Settled grain dusts were also collected from beams, rafters, and ledges of elevators. Carbohydrate contents were determined by a colorimetric assay using trifluoroacetic-acid (TFA) after hydrolysis of the grains. Protein content was measured after washing the samples with water, sodium- chloride, or sodium-dodecyl-sulfate (SDS). Attempts were made to determine the amino acid content of the dusts by thin layer chromatography (TLC). Samples were examined by light and electron microscopy. TFA hydrolysates of settled, corn, and spring wheat dusts contained 28.1, 19.1, and 22.4 micrograms per milligram (microg/mg) pentose, respectively. All dusts contained galactose. Protein contents of water washings from barley, oat, settled, and durum and spring wheat were 0.76, 0.81, 0.57, 1.42, and 1.00microg/mg, respectively. Protein contents of the SDS washings were: barley, 0.9microg/mg; oats, 0.83microg/mg; settled grain, SDS washed dusts. TLC was successful only in determining proline content of the dusts, which ranged from 0.12 to 1.45microg/mg. Each dust, except for corn, contained either husk or pericarp fragments, as well as respirable particles. Particles appeared as elongated pointed structures under the light microscope. Electron microscopy indicated the presence of small husk fragments and trichome like objects in all but corn dust. The authors conclude that the presence of protein with carbohydrate within water washings of the dusts suggests that they may contain glycoproteins.