The prevalence of specific IgE to the storage mites Aleuroglyphus ovatus (Ao) and Chortoglyphus arcuatus (Ca) was studied in 77 individuals with allergic asthma and/or chronic allergic rhinitis. All these individuals had a positive skin test (weal > or = 3 mm) to extracts of Dermatophagoides pteronyssinus (Dp) and/or Dermatophagoides farinae (Df). Sera from 29 non-atopic individuals were used as controls. A RAST was considered positive when a serum bound > or = 1% of the total counts added. The prevalence of a positive RAST to Dp was 75.3%, and to at least one of the two storage mites (Ao and Ca), 76.6%. Among patients with a positive RAST to Dp, 79.3% and 75.8% were RAST positive to Ao and Ca, respectively. RAST inhibition studies with a pool of sera from 13 subjects with high RAST binding to all three mites showed significant crossreactivity between Ao and Ca and minimal to moderate crossreactivity between Dp and Ao and Ca. This study demonstrates that sensitization to Ao and Ca is common in individuals with respiratory allergies in Cartagena, Colombia and suggests that Ao, Ca and Dp have unique and common allergenic determinants.