Phonological awareness, or the ability to detect or manipulate the sounds in words independent of meaning, has been identified as a key early literacy skill and precursor to reading. For the purposes of this review, "phonological awareness training" refers to any practice targeting young children's phonological awareness abilities. "Phonological awareness training" can involve various activities that focus on teaching children to identify, detect, delete, segment, or blend segments of spoken words (i.e., words, syllables, onsets and rimes, phonemes) or to identify, detect, or produce rhyme or alliteration. "Phonologic awareness training" can occur in both regular and special education classrooms. Various curricula are available to support this training. Two hundred twenty-five studies reviewed by the What Works Clearinghouse (WWC) investigated the effects of "phonological awareness training" on children with learning disabilities in early education settings. Four studies (O'Connor, Jenkins, Leicester, & Slocum, 1993; Sweat, 2003; Tyler, Lewis, Haskill, & Tolbert, 2003; Tyler, Gillon, Macrae, & Johnson, 2011) are randomized controlled trials that meet WWC evidence standards without reservations. Those four studies are summarized in this report. The remaining 221 studies do not meet either WWC eligibility screens or evidence standards. Four additional studies were reviewed against the pilot Single-Case Design standards. One study met the pilot Single-Case Design standards without reservations, no studies met the pilot Single-Case Design standards with reservations, and three did not meet pilot Single-Case Design standards. Studies reviewed against pilot Single-Case Design standards are listed in Appendix E and do not contribute to the intervention's rating of effectiveness. Appended are: (1) Research details for O'Connor et al., 1993, Sweat, 2003, Tyler et al., 2003, and Tyler et al., 2011; (2) Outcome measures for each domain; (3) Findings included in the rating for the communication/language competencies domain; (4) Summary of findings comparing different types of phonological awareness training for the communication/language competencies domain; and (5) Single-case design studies reviewed for this intervention. A glossary of terms is included. (Contains 7 tables, 14 endnotes and 1 additional source.