"Doors to Discovery"]TM] is a preschool literacy curriculum that uses eight thematic units of activities to help children build fundamental early literacy skills in oral language, phonological awareness, concepts of print, alphabet knowledge, writing, and comprehension. The eight thematic units cover topics such as nature, friendship, communities, society, and health. Each unit is available as a kit that includes various teacher resources. The What Works Clearinghouse (WWC) identified six studies that investigated the effects of "Doors to Discovery"[TM] on the school readiness of preschool children. The WWC reviewed four of those studies against group design evidence standards. One study (Christie, Roskos, Vukelich, & Han, 2003) is a randomized controlled trial that meets WWC evidence standards without reservations, and two studies (Assel, Landry, Swank, & Gunnewig, 2007, and Preschool Curriculum Evaluation Research [PCER] Consortium, 2008, Chapter 6) are randomized controlled trials or quasi-experimental designs that meet WWC evidence standards with reservations. Those three studies are summarized in this report. One study does not meet WWC evidence standards. The remaining two studies do not meet WWC eligibility screens for review in this topic area. Appended are: (1) Research details for Christie et al. (2003); (2) Research details for Assel et al. (2007); (3) Research details for PCER Consortium (2008, Chapter 6); (4) Outcome measures for each domain; (5) Findings included in the rating for the oral language domain; (6) Findings included in the rating for the print knowledge domain; (7) Findings included in the rating for the phonological processing domain; and (8) Findings included in the rating for the math domain. A glossary of terms is included. (Contains 9 tables and 14 endnotes.)