The Vientiane area of southern-central Lao Peoples＇ Democratic Republic (Laos) includes an extension of the Khorat Plateau Basin, which covers most of neighbouring NE Thailand. This basin contains one producing gasfield and several other-gas discoveries. The Vientiane area is in the initial stages of petroleum exploration, and no drilling has yet occurred. With the aid of new seismic data, the structure and stratigraphy, of the Vientiane area are described in relation to the region＇s tectonic history. Some aspects of this history are still poorly understood. We suggest that the age of the regional base-Khorat unconformity is Late Jurassic instead of Late Triassic as most previous studies have assumed. Recent studies have also shown that the structural inversion of the Khorat Group began in the mid-Cretaceous and not in the Tertiary. With reference to published information from petroleum exploration in NE Thailand, new data from Laos are interpreted as showing that the Vientiane area has encouraging petroleum potential. Exploration risk, which is associated with the presence and reservoir qualify of the Permian carbonates which form the primary target, is judged to be lowest in traps containing Permian palaeo-highs.