The red pulp may be called parenchyma of the spleen; it consists of sinuses of the ductal system with irregular anastomosis and pulp cords filling these irregular spaces with many cellular elements (Hirasawa and rokukiro 1970). Therefore, attempts to know the structure of the splenic red pulp had been investigated by many authors many years ago, in human (Chen and Weiss, 1972; Heusermann and Stutte, 1974; Leeson et aI., 1986), in rabbit (Roberts and Latta, 1964; Thomas, 1,967; Yamori and Mori, 1967; Burke and Simon, 1970; Snodgrass, 1973; Negm et al., 1985; EI-Awdan et al., 1989), in rat (piectet et al., 1969; Chen and Weiss, 1973; De-Bruyn and Cho, 1974; Saito et al., 1988) and in mice (Mc-cuskey and Mc-cuskey, 1985). The aim of the present work was to describe the red pulp of the rat spleen especially the reticuloendothelial cells including sinusoidal endothalial cells, reticulum cells and cordal macrophages by transmission electron microscope and relate tle recent findings to results of other studies in an effort to present a comprehensive picture of the splenic structure and function. MATERIAL