About 2.4 billion people rely on traditional biomass, mainly for cooking and heating (IEA, 2002). Essentially all of those users of traditional fuels reside in developing countries, and most of them live in rural areas; low incomes and the lack of access to alternative, modern fuels explain their choice of traditional energy supply. By the late 1990s, IEA (1998) estimated that biomass accounted for approximately 14 percent of final energy consumption, roughly on par with electricity (14 percent). It is likely that the fraction of total energy supplied by biomass will decline in the future as traditional energy carriers are supplanted by the modern movers such as electricity. This paper provides an overview of that "energy transition" from traditional to commercial fuels from the perspective of available macro-economic data. Based on the long time series data available for the United States it suggests some basic patterns in the energy transition, and it examines the transition under way in several major developing countries. It offers a simple regression model of the transition and suggests topics for further research, including an improved regression model.