The three portions of the small intestine of 18 neonatal piglets were examined by using the so-called scroll technique evolved by the authors and in cross sections. The chemical constitution and the immunoglobulin content of undigested protein droplets being under absorption were studied. An intensive absorption of immunoglobulins was demonstrated in the body of each cuticulated cylindric epithelial cell of the mucosa covering the jejunum and the proximal two-third of the ileum. Absorption was the most intensive, though variable by area, in the jejunum. It was demonstrable 4 hr after birth and reached the highest intensity between 8 and 12 hr, then tended to decline. In the protein droplets alpha-amino acids, neutral mucopolysaccharides and protein-bound Ca2+ were detected. Alkaline phosphatase activity was demonstrated around the droplets. Immunofluorescence and immunoperoxidase reactions proved the presence of immunoglobulins, first of all of IgG, in droplets. Electron microscopically, the microvilli of the involved epithelial cells were swollen, sometimes neighbouring ones were pushed away from each other; in the same areas, an electron-dense substances (colostrum) covering the enterocytes was streaming through the tubulovascular network of cells to the perinuclear region, where it appeared in spherical droplets.