Ecological risk management is increasingly being applied to marine fisheries worldwide as an aid to developing management strategies to avoid, mitigate, or manage adverse outcomes. Risk management encompasses four major steps: recognition of risk; assessment of risk; development of strategies to avoid, mitigate, manage or tolerate risk; and monitoring of risk. Here we begin the development of an ecological risk assessment for Antarctic Toothfish (Dissostichus mawsoni) longline fishery in the Ross Sea, Antarctica. We propose that, by defining risks and quantifying potential impacts, the limited research and management resources can be prioritised so as to meet the objectives of Article II of CCAMLR. Risks are considered in 4 categories: 1. Target species harvest: Risks of depletion of Antarctic Toothfish to below a level that ensures stable recruitment. 2. Bycatch species harvest: Risks of depletion of other harvested species to below a level that ensures stable recruitment. 3. Ecosystem impacts: Risks of changes to the marine ecosystem relationships due to the removal of harvested and bycatch species. 4. Exogenous effects: Risks of change in the marine ecosystem due to, or exacerbated by, exogenous effects (e.g., the introduction of alien species, effects of associated activates on the ecosystem, and effects of environmental change). The assessment of risk is based on combining the likelihood of an adverse outcome occurring and the consequence should it occur. Numerical models, such as stock or ecosystem mass-balance models can provide insights into these factors for some risks. In addition, semi-quantitative and qualitative estimates are needed because of a lack of knowledge and inability to predict the future dynamics of some parts of the system. It is also recognised that some risks (e.g., impacts of climate change) may not be able to be well predicted. The uncertainty arising from the complexity of the system and external factors acting on it means that risk management and ongoing monitoring will be required to ensure that the fishery is managed according to the conservation principles of Article II of CCAMLR.