A cross-sectional study was conducted to describe and compare sensitization patterns to common aeroallergens among paediatric patients with allergic rhinitis and asthma. 120 patients (85 boys and 35 girls), aged 3-15 years (mean age, 81 years; SD=3.4 years), attending the allergy clinic Thammasat University Hospital in Thailand and diagnosed with allergic rhinitis and/or asthma between March 1999 and February 2000 were randomly recruited into the study. Standardized skin prick tests were performed with 15 common aeroallergens. There were 63 (53%), 22 (18%) and 35 (29%) cases diagnosed with allergic rhinitis, asthma or both, respectively. The prevalence of asthma among the allergic rhinitis patients was 36%, whereas the prevalence of allergic rhinitis among asthmatic patients was 61%. The sensitization patterns for major aeroallergens among the 3 groups were similar with the most common sensitized allergens as Dermatophagoides pteronyssinus followed by D. farinae, American cockroach, Kopok and German cockroach. Among the atopic patients, a greater number of allergen reactivity was significantly associated with the increased risk of having their co-existence of allergic rhinitis and asthma (P=0.0046)