Widespread occurrence of bottom-simulating reflectors (BSRs) has been detected in multichannel seismic profiles on the upper continental slope in the southern periphery of the Orange River delta, probably indicating the presence of large quantities of gas hydrate in this area. This report is the first to show the presence of BSRs on seismic records on the southwest African continental margin south of the Walvis Ridge. Another remarkable feature in the area is the occurrence of a large number of mud volcanoes. The distribution of the BSRs and the location of the mud volcanoes are controlled by the locations of active faults. The gas hydrate in this region may consist of a mixture of microbial and thermogenic gas, whereas much of the gas flowing through the mud volcanoes probably originated from deep-seated Aptian source shales.