Landslides and erosion pose significant hazards to mining and engineering activity in the remote mountainous terrain of Western Province, Papua New Guinea. The investigation and containment of these hazards have been the concern of the Ok Tedi open-cast copper mine since engineering feasibility studies began in 1978. Subsequent terrain hazard mapping has identified numerous landslides and rock avalanche deposits in the Ok Tedi catchment and in the immediate vicinity of the mine, ranging from very low frequency, catastrophic rock avalanches through to mudslides and mudflows that recur on a daily or weekly basis. This mapping formed part of a multidisciplinary geotechnical study instigated by Ok Tedi Mining Limited and comprised detailed slope inventory, geomorphological mapping combined with air photograph interpretation nd a review of pre-existing structural geological and geotechnical data. The study area was sub-divided into 245 zones and assigned hazard and risk categories or levels derived from the field data. These classifications were presented in map form at 1:10 000 scale along with prioritized recommendations for further investigation, monitoring and remedial action, where appropriate.