This paper addresses the debate over compact fluorescent lamps and incandescent light bulbs through lifecycle analysis. It compares the environmental impacts of providing a given amount of light from incandescents and CFLs for 10,000 hours. Special attention has been paid to recently raised concerns regarding CFLs—specifically that their complex and energy-intensive manufacturing process uses so much energy that it outweighs the benefits of using CFLs, that frequently turning CFLs on and off eliminates their energy-efficiency benefits, and that they contain a large amount of mercury. The research shows that the efficiency benefits compensate for the added complexity in manufacturing;while rapid on-off cycling of the lamp does reduce the environmental (and payback) benefits of CFLs they remain a net “win,” and the mercury emitted over a CFL’s life—by power plants to power the CFL and by leakage on disposal—is still less than the mercury that can be attributed to powering the incandescent. This document concludes with tips on how consumers can maximize the environmental benefits of CFLs by using and disposing of them properly.