A model has been developed to simulate the surface of an antibody-coated schistosomulum. It consists of a layer of agar, containing antigen (tetanus toxoid) and a chemotactic factor (ECF). Some layers were coated with human anti-tetanus immunoglobulin. The mode of adherence of human eosinophils and neutrophils to these agar layers and the subsequent degranulation of the cells exactly paralleled the interaction of these cell types with antibody-coated schistosomula of Schistosoma mansoni. In particular, eosinophils made much more intimate contact than did neutrophils, and lysosomal enzymes were secreted extracellularly by direct fusion of granules with the plasma membrane of the cell. Biochemical evidence was also obtained for the secretion of enzymes during degranulation and the rate of enzyme release was found to be enhanced in the presence of specific antibody. This model, non-phagocytosable surface has the potential to provide basic information on the mode of action of effector cells in cell-mediated cytotoxic reactions against a wide range of parasites by incorporation of different factors into the agar layers.