Major federal education initiatives, including the No Child Left Behind Act of 2001, have highlighted the importance of teacher quality in improving student achievement. The federal government has committed significant funding and resources to professional development programs for teachers through Title II of the Act and other initiatives. There is limited evidence, however, of the effectiveness of professional development programs in improving teacher knowledge, teacher practice, and student achievement in reading. This report contributes to the body of research on professional development by presenting the results of an impact study of the Pacific Communities with High Performance in Literacy Development (Pacific CHILD), a professional development program designed and implemented by the Regional Educational Laboratory Pacific (REL Pacific). REL Pacific staff designed the Pacific CHILD program to improve the instruction of reading comprehension by grade 4 and grade 5 teachers and to raise student achievement in reading comprehension in the Pacific Region. Pacific CHILD is a two-year, year-round professional development intervention that combines workshops with lesson demonstrations, classroom observations, and peer learning groups. REL Pacific staff implemented Pacific CHILD between 2007 and 2010 in elementary schools in three entities in the Pacific region: American Samoa, the Commonwealth of the Northern Mariana Islands (CNMI), and Hawai'i. The study was designed to assess whether Pacific CHILD improved student achievement in reading comprehension (primary outcome) and teacher knowledge and practice (secondary outcomes) in the three entities in which it was implemented. Appended are: (1) Statistical Power Analysis; (2) Technical Notes on Impact Analyses; (3) Technical Notes on Exploratory Analyses and Results of Analysis of Impact on Teachers in Non-Hawai'i Subsamples; (4) Teacher outcome measures; (5) Student outcome measures; (6) Adaptations to design and context of implementation; (7) Exposure to Pacific CHILD by students in the impact sample; (8) Exposure to Pacific CHILD by participating teachers in the impact sample; (9) Exposure to Pacific CHILD by teachers in impact sample who were present at treatment group schools during entire intervention period; (10) Teachers' exposure to Pacific CHILD by entity; (11) Qualitative methods used to analyze adaptations to design and context of implementation; and (12) Instruments. (Contains 4 figures, 65 tables, and 139 footnotes.)