As part of a national programme on the role of inhalant allergens in respiratory allergic disorders particularly bronchial asthma in the Kingdom of Saudi Arabia, a qualitative, volumetric and immunological study of outdoor aeroallergens was conducted. Among various pollen grains and fungal spores identified,Ulocladiumspp. emerged to be one of the major spore categories in the outdoor air spora.Ulocladiumdata using Burkard volumetric sampler from three different sites for 12 months each and for 3 continuous years from one site are presented. In addition, data for 12 months for two other sites in Riyadh City using personal volumetric sampler are also presented. The peak mean weekly concentration ofUlocladiumwas highest in the populated coastal (Jeddah) with > 120 spores m-3of air. The data displayed a trend at all sites in seasonal variations showing winter with higher concentration and summer with lower concentration. The maximum concentrations for all sites fluctuated and remained under 300 spores m-3except for Jeddah reaching over 1200 m-3in late winter. The percentage ofUlocladiumin the air also varied at all sites with highest composition being 7% of the total air spora using Burkard trap and 6% using personal volumetric sampler. However, at all sitesUlocladiumwas found to be among the most frequently encountered genera. Extracts ofUlocladiumwere prepared from local isolates and tested on 100 allergic patients attending allergy clinic at investigators hospital. 13% positive SPT result with various fungal extracts including 5% byUlocladiumwere recorded in these patients. The study suggets a possible role ofUlocladiumas an allergen in the region and necessitates further investigation of the genus by inclusion ofUlocladiumantigens in allin vivoandin vitroallergy diagnostic tests in the Kingdom.