This article explores how the evidence base for aspects of early childhood has been explored using systematic research synthesis methods developed at the Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre). Three early childhood systematic reviews have been carried out using EPPI-Centre procedures and tools. The article discusses the principles underlying systematic research synthesis, the way in which the three reviews were set up, the processes involved in reviewing studies for the reviews, and the nature and generalizability of the reviews' findings. (Contains 1 figure and 3 notes.)