This article systematically reviews research on the achievement outcomes of four types of approaches to improving the reading success of children in the elementary grades: reading curricula, instructional technology, instructional process programs, and combinations of curricula and instructional process. Study inclusion criteria included use of randomized or matched control groups, a study duration of at least 12 weeks, valid achievement measures independent of the experimental treatments, and a final assessment at the end of grade 1 or later. A total of 63 beginning reading (starting in K or 1) and 79 upper elementary (2-5) reading studies met these criteria. The review concludes that instructional process programs designed to change daily teaching practices have substantially greater research support than programs that focus on curriculum or technology alone. (Contains 8 tables.)