"Ladders to Literacy" is a supplemental early literacy curriculum composed of more than 70 activities designed to develop children's print/book awareness, metalinguistic awareness, and oral language skills. The curriculum, published in the book "Ladders to Literacy: A Preschool Activity Book, Second Edition," can be used in a variety of early childhood settings and provides guidance on how teachers can adapt the activities for children with special needs. The activities are intended as models or suggestions that teachers can adopt within an existing curriculum. The What Works Clearinghouse (WWC) reviewed eight studies on "Ladders to Literacy" for preschool children. One of these studies meets WWC evidence standards; one study meets WWC evidence standards with reservations; and the remaining six studies do not meet either WWC evidence standards or eligibility screens. Based on the two studies, the WWC found potentially negative effects on oral language and no discernible effects on print knowledge, phonological processing, and math for preschool children. The conclusions presented in this report may change as new research emerges. Appendices include: (1) Study characteristics; (2) Outcome measures; (3) Summary of study findings included in the ratings; (4) Summary of follow-up findings; (5) "Ladders to Literacy" ratings; and (6) Extent of evidence by domain. (Contains 7 footnotes.)