AIM: The DH91 seismic survey programme was designed to provide new 2D coverage of potential prospects and leads in an offshore area with very little modern seismic data, especially in the southeastern part of the permit. Complementary 1983 and 1984 seismic from the central part of EPP 25 was reprocessed as part of the 1991 programme. METHODS: Survey dates: 17/5/91 - 28/7/91. Energy source: Airgun. CDP coverage: 6000%. Recording mode: 240 channel digital - LRS 16A Kiloseis marine streamer recording system. SP interval: 26.66 metres, group interval: 13.33 metres. Of a total 7541.5 line km of semi-detailed and detailed seismic data recorded for the DH91 survey, 104 lines in EPP 25 totalling 3927.63 line km, and 78 lines in EPP 26 totalling 3613.87 line km, were shot by Party 86 of contractor Western Geophysical Company using the M/V Western Odyssey, and processed in Sydney by Simon Horizon Australia. Seismic interpretation was performed by operator BHP Petroleum. RESULTS: In-house interpretation on a Landmark computer workstation of the permit Year 1 DH91 survey data, done in conjunction with that of 3121 line km of older 1993/94 data reprocessed by BHP, resulted in the mapping in time of 7 key regional marker horizons, and has clearly revealed the highly varied structural and stratigraphic character of the entire Duntroon Basin. A number of good new structural prospects and leads were identified at various stratigraphic levels, and it is intended to try to upgrade these during the permit Year 2 seismic programme. The reprocessing work achieved a significant improvement in data quality, allowing confident data matching for those areas not covered by the DH91 grid.