Study of helminth antigens with a special reference to Schistosoma are reviewed, not exhaustively but rather as an overview of trends. These antigens are considered at four levels. Firstly, characterization and utilization of genus, species or stage-specific antigens should improve the efficiency of immunological diagnosis of helminth diseases. Then, some well-characterized antigens are of interest because of their involvement in the modulation of the immune response or in the immunopathological field. Finally, identification of relevant antigens capable of eliciting a protective immune response is a prerequisite to any attempt at immunoprophylaxy of helminthic infections.