This thesis reviews the state of knowledge on geology, structure and tectonic evolution of West Antarctica. An airborne geophysical survey in West Antarctica comprising simultaneous Radio Echo Sounding (RES) and magnetics was carried out over -1 M km$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ of the ice covered area. The collection and reduction of large volumes of RES and magnetic data are described. The first detailed maps of ice sheet surface and bedrock topography were compiled from the RES data and are presented. The main characteristics of the West Antarctic ice sheet and its stability are briefly discussed including the grounding zone of the Ronne-Filchner Ice Shelf. Calculations for the depression of the crust by the weight of the overlying ice sheet are made and the bedrock topography isostatically adjusted. Detailed comparisons of magnetic profiles with the bedrock topography are made. Depth determinations on the magnetic profiles were performed and selected anomalies are modelled by computer to give quantitative estimates of bedrock magnetisations. These data together with other pertinent geophysical data are discussed and interpretations of subglacial geology made. Discussion concentrates on defining boundaries between major structural units in West Antarctica and the boundary between East and West Antarctica. The tectonic evolution and position of West Antarctica in Gondwanaland is discussed in the light of these interpretations. West Antarctica is thought to comprise several microcontinental fragments which have moved relative to each other during the breakup of Gondwanaland.