We have isolated, characterized and quantified the immunocompetent cells present in the extravascular hepatic compartment at various stages after Plasmodium yoelii malaria infection with sporozoites. Cytological analyses revealed a predominantly lymphoid population. In mice with a primary infection, the predominant cells were CD4+, CD8+ and B lymphocytes. In fully protected mice, CD3+ CD4- CD8- and polymorphonuclear cells, particularly eosinophils, were most common. The significance of changes in subpopulations is discussed in relation to antigen presentation and host-protective mechanisms.