The Critical Appraisal of light-emitting-diode (LED) curing lights published in 2003 found that early first-generation LED curing lights did not meet manufacturers' claims and required exposure times twice as long as conventional quartz-tungsten-halogen (QTH) curing lights to adequately polymerize resin composites. This Critical Appraisal reviews a sample of the recently published research on the performance of the latest generation of LED curing lights.