This study reports on an evaluation of the "Reading Partners" program, which uses community volunteers to provide one-on-one tutoring to struggling readers in underresourced elementary schools. Established in 1999 in East Menlo Park, California, the mission of "Reading Partners" is to help children become lifelong readers by empowering communities to provide individualized instruction with measurable results. This report builds on those initial findings by describing the "Reading Partners" program and its implementation in greater detail, exploring whether the program is more or less effective for particular subgroups of students, and assessing some of the potential explanations for the program's success to date. In addition, this report includes an analysis of the cost of implementing the Reading Partners program in 6 of the 19 sites. The following are appended: (1) Implementation Study Methods; (2) Impact Study Methods and Teacher Survey; (3) Tutor Background Characteristics and Additional Impact Findings; (4) Cost Study Methods; and (5) Additional Cost Findings. [This report was written with A. Brooks Bowden and Yilin Pan.]