The present report describes ultrastructural and surface features of hepatic Kupffer cells, with particular emphasis on the characteristics of these cells in suspension, as seen under the scanning electron microscopy (SEM), after their successful isolation by pronase digestion of liver tissue. Kupffer cells were readily recognized in sections of the liver examined by transmission electron microscopy, particularly after tagging by carbon, heat-damaged erythrocytes, and latex spheres. Their ultrastructural features in suspension and in liver sections were similar to those described for peritoneal macrophages. In the present study, a high yield of well-preserved Kupffer cells was obtained after selective enzymatic digestion of intact rat liver. Kupffer cells were readily distinguished from lymphocytes and hepatocytes on the basis of their surface architecture, and showed transverse ridge-like profiles and ruffled folds which became more prominent during phagocytosis. The sequence of events during the various stages of latex bead phagocytosis was well visualized with the SEM. Kupffer cells in suspension, during spreading and attachment to glass and during phagocytosis, resembled peritoneal macrophages isolated from rats, providing further evidence that these cell types are closely related.