Abstract Rising demand and the depletion of its offshore reserves has resulted in the UK becoming a net importer of natural gas. An increased reliance on imports and limited current storage availability mean that the UK faces increasing energy bills and risk of disruption to supply. Because of this the UK government has set about ensuring security of energy supply. Steps taken include the construction of major new pipelines from Norway and Holland and improvements to interconnectors in the southern North Sea. The Government also recognizes that improvements to the gas supply infrastructure are required, including the need for significant increases in gas storage capacity; best met by the construction of underground storage facilities. Focus on energy security has also raised the likelihood of a new generation of coal-fired power-stations. For such a step to be environmentally viable, clean-coal technologies with near-zero greenhouse gas emissions will be required. Underground CO 2 storage will be a key element of this strategy. This volume reviews the technologies and issues involved in the underground storage of natural gas and CO 2 , by means of case-studies and examples from the UK and also from overseas. The potential for underground storage of other gases such as hydrogen, or compressed air linked to renewable sources is also reviewed.