Students in U.S. public schools have consistently recorded substandard scores on measures of school performance in mathematics. This substandard performance could adversely affect the nation's future economic competitiveness, growth, and welfare. Educational and political leaders have sought school reforms that will result in U.S. students scoring as well on measures of academic achievement as students in other industrialized nations with minimal success. This quantitative, quasi-experimental study used a nonequivalent control group pretest-posttest design to determine the effectiveness of Virtual Manipulatives (VMs) for teaching mathematics and mathematics performance. The convenience sample consisted of two groups of fifth graders (n = 139) attending an urban public elementary school in Georgia. Each group received mathematics instruction from the same teacher, but instruction in one group also included the use of VMs. The STAR Math Test, Version 2 (SMT2) was used as the pretest and posttest. A Kruskal-Wallis and a Mann-Whitney U were used to test the null hypotheses related to mathematics performance and the use of VMs, and the use of VMs controlling for age and gender. Results indicated that there was no significant difference in gain scores between the intervention and comparison groups, z = -1.33, p > 0.05, with neither group scoring significantly higher than the other, and gender, x[superscript 2] (3, 139) = 2.11, p > 0.05, with neither group scoring significantly higher than the other. No significant difference was found between groups controlling for age, x[superscript 2] (3, 139) = 3.75, p > 0.05, and neither of the two age groups scored significantly higher than the other. The use of VMs has been used to the benefit of mathematics instruction, although no statistically significant difference was found between pretest and posttest scores of the two groups in this study. Future studies of VMs should include longer periods for their use to maximize the possibility of effects. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]