AIM:To extend by seismic reflection profiling along tie-lines the information gained from previous offshore and onshore reflection and refraction work, thereby aiding in establishing the basin configuration and determining whether any prospective structural trends are present.METHODS: Survey dates: 21/10 - 25/11/67. Energy source: explosives. CDP coverage: 300%. Recording mode: 30 channel digital - SDS 1010 recorder. SP interval: 912 feet; group interval: 133 feet.RESULTS:5 lines totalling 379.3 line miles were acquired in SA waters by Party 86 of Western Geophysical, and processed in Houston, Texas by that company. Another 5 lines totalling 364.7 line miles were also acquired in WA waters by this survey, but are not contiguous to the SA lines. Seismic interpretation of all the data recorded in both the 1967 offshore Eucla Basin surveys was performed in Sydney by Tenneco. Data quality over the SA portion of the survey was poor to good, the poorer data being associated with the shallower, inshore sedimentary section. A 7500 feet/second interval velocity, derived from analysis of stacking velocities, was used to convert the section times to subsea depths. Two reflecting horizons seen beneath the base Tertiary regional unconformity, thought to be a near top ?Cretaceous sandstone horizon and a near ?weathered Precambrian basement horizon, were mapped in depth across both the WA and SA portions of the basin. Thickness of sediments is estimated to range from 700 to 6000 feet over the survey area, with an average thickness of less than 3500 feet. The shallow-depth section, for the most part, is unaffected by deeper faulting, and reveals no significant stuctural developments. The deeper, near basement reflecting horizon exhibits definite NE-SW structural trends and faulting, the most apparent feature being a broadly thickening zone of ?Palaeozoic strata extending from the shore into the deeper water part of the Bight near the middle of OEL 33. However, these interpretations are based on what is still very sparse geophysical control.