This article reports the effects of a 2-year supplemental reading program for students in kindergarten through third grade that focused on the development of decoding skills and reading fluency. Two hundred ninety-nine students were identified for participation and were randomly assigned to the supplemental instruction or to a no-treatment control group. Participants' reading ability was assessed in the fall, before the first year of the intervention, and again in the spring of Years 1, 2, 3, and 4. At the end of the 2-year intervention, students who received the supplemental instruction performed significantly better than their matched controls on measures of entry-level reading skills (i.e., letter?word identification and word attack), oral reading fluency, vocabulary, and comprehension. The benefits of the instruction were still clear 2 years after instruction had ended, with students in the supplemental instruction condition still showing significantly greater growth on the measure of oral reading fluency. Hispanic students benefited from the supplemental reading instruction in English as much as or more than non-Hispanic students. Results support the value of supplemental instruction focused on the development of word recognition skills for helping students at risk for reading failure.