Geological studies of the islands on the Seychelles Bank, and the results of seismic refraction experiments made on the bank, are reviewed. They show that the crust is of continental type under the centre of the bank. Gravity measurements confirm that the thick crust extends to the northern edge of the bank and show that the Mohorovicic discontinuity slopes upward at an angle of about 19 degrees under the peripheral cliff. Large narrow magnetic anomalies occurring in the central area of the bank are ascribed to minor intrusions of dolerite found in the Precambrian granites, and it is suggested that the edge of this area may mark the limit of the granite mass. Magnetic anomaly profiles of the Mascarene Ridge are similar to those over the Seychelles Bank and could result from a similar structure.