Four media are used to isolate enterocytes from the jejunum of the mouse (basic medium with either hyaluronidase, dispase, pronase, or EDTA). During incubation the intestinal wall is gently agitated. Layers of epithelial cells rather than single cells are removed from the mucosal surface by these procedures. Small groups of enterocytes and single cells can be obtained by further mechanical agitation, e.g. by repeatedly washing the isolated epithelia. Similar morphological findings (transmission and scanning electron microscopy) are obtained after using the various isolation media. Only with EDTA a dilatation of the endoplasmic reticulum is regularly seen. Isolation of the enterocytes starts from the tip of the intestinal villus. The straight apical surface becomes convex and the most lateral microvilli of the brush border desintegrate. The opening of the terminal bars can be observed. Surface differentiations on the lateral cell surfaces of isolated enterocytes become less obvious and disappear. This is discussed with respect to the so-called "lateral vacuoles" which appear in isolated enterocytes. Large spherical protrusions are developed at the basal surface of enterocytes. The cell membrane covering these protrusions is frequently found to be discontinuous. No other cell organelles than ribosomes are to be seen inside of these protrusions. Membrane-bound vesicles are also frequently seen. It is suggested that the basal spherical protrusions are casted off.