The main features of magnetic anomalies over ocean ridges have been explained1 as a corollary of seafloor spreading and geomagnetic reversals. Oceanic crust is formed in a narrow region, becoming magnetized in the direction of the Earth's magnetic field as its temperature falls through the Curie point of the magnetic minerals present. The Gulf of Aden was one of the first places where reversely magnetized sea floor was recognized2. The seafloor spreading direction and latitude are such that the anomaly due to normal magnetization is negative and slightly skewed. Positive anomalies were also observed suggesting the presence of reverse magnetization. A short wavelength magnetic anomaly which frequently occurs superimposed on the axial magnetic anomaly in the Gulf of Aden is now described. Various interpretations are considered; the preferred involves a dramatic shallowing of the Curie temperature isotherm close to the seafloor spreading centre. The interpretation has implications for models of the generation of oceanic lithosphere and for locating possible geothermal areas in rifted regions.