Cajal interstitial cells are cells that are found in the abdominal digestive system wall, between neurons and smooth muscular tissue. They are considered to be pacemakers for slow intestinal waves. The paper discuss about the electron-microscopic identification of Cajal interstitial cells in the rat small intestine wall, cell morphology, placement of these cells in the muscular layer and the relation between Cajal interstitial cells and the components of the nervous plexus. Fragments of rat small intestine have been prepared for electron microscopy examination. Cajal interstitial cells have been found in different locations: in the circular muscular layer, around the nervous nodes and between the muscular layers (longitudinal and circular). The main morphologic characteristic of these cells is the aspect of cytoplasm, with numerous vacuoles and long extensions, some of them very thin, with a tendency to divide. Some Cajal interstitial cells form a network that surrounds the nervous nodes. Other form junctions with the muscular cells and with the interstitial neurons.