Hemoglobins of the Diptera (insect) family Chironomidae have been identified as causative allergens in asthmatic patients. In this study, 229 Japanese, 17 Taiwanese, and 92 Swedish sera from atopic patients were tested for antibodies against Chi t I, the hemoglobin from the European midge species Chironomus thummi, and against crude extracts from the Japanese midges Tokunagayusurika akamusi (T. akamusi) and Cricotopus sylvestris (Cr. sylvestris). Nearly 40% of patients showed a positive reaction to Cr. sylvestris extract, which contains no hemoglobin. This result is probably due to the presence of other partially cross-reacting allergens than hemoglobin. Nearly all tested Japanese serum samples showed cross-reactivity between Chi t I and Cr. sylvestris, a finding which is evidence for common epitopes in both midge species. Furthermore, an overall good correlation between the amounts of IgE antibodies against Chi t I and Chi t I component III was found in sera from Swedish, Japanese, and German patients.