In this paper, the authors review the latest situation of risk assessment research efforts on to "Carbon Dioxide Geological Storage (geological CCS)" technology. After publication of the special report on geological CCS (2005) with sections about risk assessment, significant progresses have been achieved in risk assessment as technological evaluation of geological CCS as one of likely greenhouse gas discharge reduction measure. Those efforts produced permission scheme or safety guideline for geological CCS in some countries. On the other hand, as regard with research and development for precise risk assessment and management of CO2 Geological Storage, it is on the halfway of establishing methodologies. To establish quantitative assessment methodology for rational and reasonable risk governance of this field, the following additional research and development efforts are still urgently required: hazard data collection, data preparation for evaluation about surface facilities and surface local environment, and establishing methodology for uncertainty treatment of geological formation.
