The purpose of this study was to evaluate the impact of Jumpstart, a supplemental early literacy intervention, on preschool-age children from low-income backgrounds. Participants consisted of 74 low-income children from three preschools and child-care programs. Thirty-three children were randomly assigned by Jumpstart to the treatment group and 33 children were assigned to the same-classroom comparison group. Treatment and control children were from the same classrooms. An additional 8 children were selected for an attention-control group. To determine if children receiving a combination of Jumpstart and their preschool curriculum would demonstrate greater cognitive and social-emotional gains than child than children who only received preschool curriculum, this study used a field-experimental, short-term longitudinal design, with data collection occurring in the fall of 2007 and the spring of 2008. An environmental quality assessment was completed in each setting. Findings indicated that pre-to posttest gains in early literacy and school readiness were significantly greater for Jumpstart children than for same-classroom comparison and attention-control children. Jumpstart children also made significantly greater gains in social/emotional functioning than same-classroom comparison children. One unexpected finding was that although children in the attention-control group did not make significant gains in early literacy or school readiness, they did gain significantly in social/emotional adjustment, more so than children in the treatment and same-class comparison groups. This finding is significant, as it demonstrates the importance of one-on-one adult attention for economically at-risk children. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]