The key issue in the decommissioning of nuclear facilities is the progressive removal of hazards, by stepwise decontamination and dismantling activities that have to be carried out safely and within the boundaries of an approved safety case. The decommissioning safety case is a collection of arguments and evidence to demonstrate the safety of a decommissioning project. The safety case involves analysing the hazards and the separate stages required for hazard reduction. This status report, drawn from the activities of the OECD/NEA Working Party on Decommissioning and Dismantling (WPDD), will be helpful to individuals and organisations involved in the preparation of a decommissioning safety case.