Various antigens interacting specifically with Ig[immunoglobulin]E antibodies from infected humans were identified in S. mansoni, F. hepatica and E. granulosus soluble extracts by means of radioimmunoelectrophoresis. Two allergens common to adult worm and cercariae were identified in S. mansoni extracts. They were distinct from genus or species specific antigens previously identified in the parasite. In adult F. hepatica extract, a species-specific antigen and another lipoprotein interacted with IgE antibodies of patients with fasciolasis. Two major allergens were found in whole fluid of sheep E. granulosus cysts. One of them corresponded to Echinococcus genus specific antigen. These results are discussed in relation to immunological findings in parasitic infections.