Skin prick tests with 14 selected local aeroallergens were performed on 100 asthmatic children aged 0-16 years attending the Pediatric Allergy Clinic, Faculty of Medicine, Siriraj Hospital. The 14 allergens included Dermatophagoides farinae, Dermatophagoides pteronyssinus, American cockroach (Periplaneta americana), Johnson grass (Sorghum halopense), Cladosporium clarosporoides, Alternaria tenuis, Penicillium mix, Aspergillus mix, cat dander, dog dander, milk, egg white, soy and shrimp. Positive skin test reactivity was defined as a mean wheal diameter > or = 3 mm at the 20 minute reading. There were 68 males and 32 females. Their ages were between 0-2 years (n = 1), 2-5 years (n = 19), 5-10 years (n = 49) and 10-16 years (n = 31). Of all the subjects, 22 were classified as having mild asthma, 74 with moderate asthma and 4 with severe asthma. At least one skin prick test was positive in 74 subjects (74%) and two positive tests in 66 subjects (66%). The prevalence of sensitization to various allergens was as follows; Dermatophagoides pteronyssinus 67%, Dermatophagoides farinae 62%, American cockroach 44%, shrimp 14%, Johnson grass 14%, cat dander 10%, Alternaria 7%, Cladosporium 7%, dog dander 5%, soy 4%, Penicillium 3%, Aspergillus 2%, milk 2% and egg white 1%. The wheal size to Dermatophagoides pteronyssinus did not correlate with age. In this group of asthmatic Thai children, house dust mites are the most important allergen causing sensitization.