Magnetic data over the southern Red Sea are used to examine various models for the evolution of the region. The linear nature of the magnetic anomalies over the coastal margins and adjacent portions of the main trough together with their decrease in amplitude with elevation is shown to be compatible with deep, thin sources that are strongly magnetized. The general lack of correspondence between gravity anomalies and deskewed magnetic anomalies indicates that the anomalies are due to intrabasement bodies rather than basement relief associated with density contrasts. Across-axis correlations of individual anomalies indicate a symmetrical disposition of magnetic sources about a line close to the present deep water axis. The regular, symmetrical pattern of linear anomalies strongly suggests a seafloor spreading origin. The combined geologic and geophysical evidence, therefore, supports a model in which the margins are underlain by material more typically oceanic in character than continental. The magnetic evidence further implies that this oceanic crust formed during an earlier phase of spreading in the Red Sea. Although the age of this crust is unknown, anomaly correlations suggest spreading may have taken place during the Late Oligocene-Early Miocene. ¿ American Geophysical Union 1989