Landfill gas (LFG) is a flammable and potentially harmful mixture of methane, carbon dioxide and a large number of trace constituents produced when waste decays in landfill disposal sites. The need to prevent damage from landfill gas emissions has been recognised since the 1970s, and is now enshrined in landfill site regulations. Sophisticated gas control measures such as actively-pumped gas extraction wells and multi-layered liners are now being implemented on a wide scale. The exploitation of LFG as a fuel or feed stock can complement the objectives of environmental protection and, at the same time, provide an additional revenue stream and reduce the use of fossil fuels. Exploitation of landfill gas in the UK began in the early 1980s, initially as a replacement fuel in kilns and boilers. There are now 13 such direct use projects saving the energy equivalent 50,000 tonnes of coal per year (January 1993). Use of LFG for power generation began in 1985. Government support for electricity from renewable sources has made power generation the dominant use for LFG in the UK. The UK currently has 42 power generation projects with a combined capacity of 72 MWe, saving the energy equivalent to 263,000 tonnes of coal per year (January 1993). This paper reviews current understanding of the processes of landfill gas formation and outlines the considerations required for its use as a fuel. The paper outlines the technology of gas collection and exploitation and assesses the economics of generating electricity from LFG in the UK, and the scope for further development.