Singapore is a unique blend of a tropical environment with a high standard of hygiene and public health care. The objective was to define the prevalence, clinical characteristics, and environmental risk factors of specific aeroallergen sensitization in pediatric allergic rhinitis patients in this unique environment. The method adopted was a retrospective analysis of allergic rhinitis patients, undergoing aeroallergen skin prick testing (SPT), in the outpatient specialty clinic of the KK Children's hospital, from July 2001 to June 2002. A total of 202 patients were included, 161 (80%) males, 167 (83%) Chinese, age mean 7.6 yr (range 2–14 yr). The most prevalent clinical symptoms were: watery rhinorrhea 61%, blocked nose 61%, sneezing 52%, snoring 17%, and epistaxis 12%. SPT results were positive for house dust mites in 97% of children, pets (20%), molds (19%), pollens (15%), and kapok (10%). Mold sensitization was significantly more prevalent in households without air-conditioning (aircon), 49% vs. 10% with aircon (odds ratio 9.4, 95% CI 3.8–22.9). Polysensitization (sensitization to three or more allergens) was similarly more prevalent in households without aircon, 51% vs. 14% with aircon (odds ratio 6.4, 95% CI 2.8–14.7). It was concluded that indoor aeroallergen sensitization is the major associated factor with clinical allergic rhinitis in children in Singapore. Patients living in households without air-conditioning are at increased risk of mold sensitization and polysensitization.