From Oct. 1959 to Nov. 1960, 17 24-hour and 1 48-hour series of continuous samplings were made. Both silicone slides for fungus spore counts and nutrient plates for identification of colonies were exposed in slit samplers each hour through the sampling period. A 2nd silicone slide was exposed each hour to test the viability of the spores. These slides were incubated in a moist chamber and the germinating spores were counted directly. A few fungi displayed diurnal periodicity but most did not. Basidiospores, 1-and 2-celled hyaline spores, Fusarium colonies, yeasts, and hyphal fragments had a nighttime peak, with smuts a light daytime peak. No definite peaks were observed for Cladosporium, Alternaria. Cercospora. and rust. Cladosporium spores and colonies sometimes had peaks during the day, other times at night, but there was no consistent pattern. Spore viability varied on the average from 42 to 57% with some indication that germination was lowest in the afternoon and highest in the early morning.