The paper discusses technical issues associated with the use of landfill gas (LFG) compared with natural gas--which is the primary fuel used for energy conversion equipment such as internal combustion engines, gas turbines, and fuel cells. LFG is a medium-heating-value fuel containing trace constituents that require gas pretreatment and energy equipment modifications to operate successfully. There are more than 100 LFG-to-energy projects in the U.S., and their developers and operators have found different ways to minimize the potential problems associated with LFG utilization. The paper also gives an overview of developers and operators of these projects, data of European projects, non-technical issues such as project barriers and incentives, the relationship between LFG delivery and energy output, active landfill gas developers, and insights on project decision making.