The deep structure of the high-grade Limpopo belt and the low-grade Kaapvaal craton has been studied by means of deep geoelectrical soundings as well as the analysis of gravity and magnetic data. In the low-grade granitoid terranes the upper 6–10 km of the Archaean crust is characterized by high resistivity rocks (40 000–100 000 Ω.m) overlying a moderately resistive zone (∼ 5000Ω.m) that extends to about the crust-mantle boundary. Below this occurs a conductive zone (1–100 Ω.m) followed by a resistive zone in the upper mantle. In the high-grade Southern Marginal Zone and Central Zone of the Limpopo belt the uppermost high resistivity zone of the crust is absent, and the about 5000 Ω.m material extends to the surface. The combined geoelectrical and gravity data set indicates that at the southern boundary of the Southern Marginal Zone the high-resistivity upper crustal rocks characterizing the low-grade terrane to the south, dip northward underneath the moderately resistive high-grade rocks. Geoelectrical and gravity modelling shows that the more than 400 g.u. isostatic anomaly over the Southern Marginal Zone of the Limpopo belt is caused by dense middle to lower crustal material in the upper 10 km of the crust. Geoelectrical and gravity studies prove that the Archaean greenstone belts are shallow features rarely exceeding 7 km in depth, and these structures are therefore confined to the high resistivity zones in the low-grade terranes. The geophysical surveys proved that over a large area sheet-like granite bodies cover mafic to ultramafic rocks of the Barberton belt.