The coelomic cavities are covered with serosal membranes: peritoneum, pleura, pericardium and tunica vaginalis testis. The present review compiles data, on their normal structure, development and involvement in pathologic processes. The authors add also results on the ultrastructure of the parietal pleura, peritoneum and pericardium and visceral sheets of the different organs as well in transitional areas between them in man and experimental animals (rat, cat, rabbit, guinea pig, mouse, ground squirrel). By transmission and scanning electron microscopy they distinguish three basic types of relief on both serosal sheets, organs and their different regions. The authors provide a comprehensive description of the main components of the SM involving: mesothelium, an underlying basal lamina and submesothelial connective tissue layer.