The intimal synovial surface in normal conditions, using a scanning electron microscope, has been studied. The three synovial membrane types are clearly recognizable: fibrous (Fig. 8), adipose (Figs. 9 and 10) and areolar (Figs. 1 and 2); but only in the areolar type, the characterization of the main two cellular types: synoviocytes B and A, is possible. Synoviocyte B represents the constitutive element which characterizes the synovial intima; it has a cellular body of irregular shape and long cytoplasmic processes directed towards the joint cavity (Figs. 3, 4 and 5). The cellular body and the cytoplasmic processes are covered by small blebs (Fig. 6). and similar vesicles, probably of the same cellular origin, are scattered throughout the extracellular matrix. These cells are likely responsible for the specific structure of the interstitial tissue adapted to the exchanges and to the regulation of the composition of the synovial fluid (Okada et. al. 1981; Linck and Porte, 1978, 1981). Synoviocyte A is a small minority; it has many long and irregular membrane infoldings which define a complicated system of intracellular canaliculi of various depth (Fig. 7). The ultrastructural characteristics of their surface and the peculiarity of their organelle apparatus, described by other AA. (Fell et. al., 1976), demonstrate that these elements carry out a macrophagic function. The clear majority of the synoviocytes B in the intimal surface suggests that in normal conditions, the synthesizing processes prevail over the phagocytosis ones.