The composition of airborne bacteria and fungi at Helwan district were studied using slit sampler. The diurnal variations of airborne bacteria and fungi could be divided into four periods: 1)the morning maximum concentration (6am-10am), 2)midday to afternoon pattern (10am-4pm), 3)the evening concentration peak (6pm-8pm) and 4)the night time gradually decreased concentration (10pm-12am). Aspergillus, Penicillium, Alternaria and Cladosporium were the most predominant fungal genera in the air. Aspergillus showed double peak pattern, whileas, Penicillium, Alternaria and Cladosporium showed...