Experiments were conducted in 1977 and 1978 on vertical variation of spore concentrations in the atmosphere at 1.5, 9, and 30 m heights with volumetric samplers, which were located at the Rocky Ford Experimental Farm, located 3.2 km north of Manhattan, Kansas city limits (USA). This farm contained turf and grain crop research plots, with general field crops and tallgrass prairie between site and city limits. Spore counts were significantly higher at the 1.5 m height than at either other height when adequate moisture supported local spore production. Spore counts from the 9 and 30 m heights never differed significantly from each other. When moisture was insufficient to sustain spore production locally, all spore forms were uniformly distributed vertically in the atmosphere to the heights studied. In such cases, the major part of the airspora consisted of spores transported in the atmosphere from remote sources.