Mechanisms of eosinophil response induced by soluble egg antigen (SEA) in Schistosoma japonicum-infected guinea pig tissues were analyzed using two purified components of SEA: major allergenic components (JEAL) and a major eosinophil chemotactic component (ECF-SjE). Eosinophil response to the crude SEA of S. japonicum was detected at the injection site mainly at 2-8 h after the antigenic challenge; this response consisted of two different phases of eosinophil attraction. An early phase (2 h) was mediated by an immediate-type hypersensitivity reaction; JEAL played an important role in mediating this phase of eosinophil response. A late phase (8 h) was mediated by ECF-SjE. Therefore, this phase of eosinophil response was caused by direct eosinophilotactic activity of SEA. These two types of eosinophil response must be important processes in the formation of S. japonicum egg-associated eosinophilic granuloma.