The author compares the young Pre-Cambrian rocks of the Red Sea area. On the basis of paleontological and radioactive age-determinations he comes to the conclusion that in this area the rocks belong to the youngest consolidated rim (abt. 600 m.y.) of the old African cratonic shield (abt. 3 000 m.y.), equal to the Riphean (Schatsky). Two geosynclines or two parts of one geosyncline with plenty of basic volcanics, pillow lavas and serpentines have been mapped by Glen Brown in western Saudi Arabia (250 km length) and by the Geological Survey of Egypt in the central part of the Eastern Desert (100 km length). In Saudi Arabia the young Pre-Cambrian section is over 20 km thick and in the central part of the Eastern Desert of Egypt about 12 km. There is a change in facies from submarine ophiolites in the trough to partly subaerial volcanics on the block-faulted rim of the trough. The sedimentary section is mainly pelitic and psammatic. Limestone (marble) is rare or absent. The tectonic trends are probably influenced by older highs. In the northern part of the area the general trend is often across the Gulf of Suez. In the central and southern part of the Red Sea a strike roughly N—S predominates, but some E—W trends occur too, as in Hadramaut, Eritrea and Eastern Somaliland.