Nuclear explosions in South Australia at Maralinga in 1956 and 1957, and at Emu in 1953, provided unique opportunities for determining accurately seismic velocities in the crust and upper mantle. Stations south and south‐east of Maralinga towards Adelaide gave P velocities of 3.4 km/sec in thin sediments, 5.8 km/sec in the upper 1–2 km of “granitic” material just below the sediments, and 6.3 km/sec (P1) for deeper granitic material which probably makes up much of the crust. S1 (Lg) velocity was 3.59 (±0–01) km/sec, Pn in the upper mantle was 8.05 (±0.04) km/sec, appreciably lower than previously found west of Maralinga, and Sn 4.61 (±0.04) km/sec.