A structural and kinematic analysis of the peridotites and associated gneisses on Zabargad Island in the Red Sea indicates a rift setting and not a transform setting, because the foliations in the peridotite trend NW--SE and are vertical, and the stretching lineations plunge 50¿NW. A clear distinction can be made between a higher-T structure developed mainly in feldspathic therzolites and characterized by dextral shear flow and a lower-T to mylonitic structure developed at hydrous conditions (syntectonic amphiboles) and characterized by sinistral shear flow. The first structure is ascribed to a diapiric mantle upwelling. The dextral shear sense suggests that the island originated on the western limb of the diapir. Flow lines are not vertical, but moderately inclined; this seems to be a consistent feature of asthenosphere flow beneath rifts. The low-T deformation records the final emplacement of the peridotites into the crust, represented by mafic gneisses as also these gneisses are affected by it. The metamorphism of the gneisses dated as lower Miocene (K/Ar amphibole in amphibolite) is, at least partly, the result of their juxtaposition with the hotter peridotites. Thus, the intrusion of the mantle diapir coincides with the early rifting of the Red Sea. The sinistral shear flow in low-T peridotites and gneisses could be related to the sinistral component of lithospheric stretching during the Red Sea rifting. ¿ American Geophysical Union 1986