Aerobiological studies to evaluate allergenic fungal spores in the atmosphere of Riyadh were conducted. Burkard personal volumetric sampler were operated as volumetric ‘viable' spore traps at two different sites (Al-Batha, a more developed area in the south and Al-Ulia, a less developed area in the north) in Riyadh. Twice a week samplings were carried out over a period of 12 month. The seasonal fluctuations of the most frequent fungi were plotted as ‘major' components. The dominant species at the two sites were members of the genera Alternaria, Aspergillus, Cladosporium, Penicillium and Ulocladium. Drechslera, Fusarium, Rhizopus and Stachybotrytis species were minor components or sporadic. Seasonal variations of the total colonies were significantly (p < 0.05) different. They showed higher concentrations in the winter season and the lowest in summer. The Al-Batha site was always higher in spore concentrations than the Al-Ulia site. The results provide valuable information for the diagnosis and prophylaxis of allergic diseases due to airborne fungi.