The processing of ovalbumin by isolated rat enterocytes and by splenic adherent cells (SAC) was compared. Paraformaldehyde fixation blocked presentation of ovalbumin to T cells by both cell types when given before, but not after, an antigen pulse. Presentation of ovalbumin by both cell types was blocked by treatment with chloroquine, ammonium chloride or monensin before the antigen pulse. Leupeptin treatment before the antigen pulse inhibited presentation by SAC, but not by enterocytes. Ovalbumin processed by enterocytes was not presented by fixed SAC. Radiolabelled ovalbumin was degraded to small molecular weight fragments by SAC, but not by enterocytes. It is suggested that, compared to the degradative processing seen in macrophages. B cells and dendritic cells, processing of ovalbumin by enterocytes comprises a more subtle, non-degradative mechanism.