The authors' purpose was to explore the effects of a supplementary, guided, silent reading intervention with 80 struggling third-grade readers who were retained at grade level as a result of poor performance on the reading portion of a criterion referenced state assessment. The students were distributed in 11 elementary schools in a large, urban school district in the state of Florida. A matched, quasi-experimental design was constructed using propensity scores for this study. Students in the guided, silent reading intervention, "Reading Plus," evidenced higher, statistically significant mean scores on the Florida Comprehensive Assessment Test criterion assessment measure of reading at posttest. The effect size, favoring the guided, silent reading intervention group was large, 1 full standard deviation, when comparing the 2 comparison groups' mean posttest scores. As such, the results indicate a large advantage for providing struggling third-grade readers guided silent reading fluency practice in a computer-based practice environment. No significant difference was found between the treatment and control group on the Stanford Achievement Test-10 (SAT-10) posttest scores, although posttest scores for the treatment group trended higher than the control. After conducting a power analysis, it was determined that the sample size (n = 80) was too small to provide sufficient statistical power to detect a difference in third-grade students' SAT-10 scores. (Contains 2 tables.)