The purpose of this study was to explore the impact of the Problem Based Learning (PBL) units developed by a large suburban school district in the mid-Atlantic for the middle school gifted science curriculum on: a) students' performance on standardized tests in middle school Science, as measured by a sample of relevant test questions from a district-managed test bank; and b) students' perceptions of classroom quality according to the constructs of: meaningfulness, challenge, choice, self-efficacy, and appeal as measured by the Student Perceptions of Classroom Quality scale (SPOCQ) (Gentry & Owens, 2004). A group of students taught using PBL and a comparison group of students taught using traditional instruction were studied. Between the two groups, a total of 457 students participated in the study. Pre and post student achievement data were collected using a 25 item multiple choice test that aligned with state and local objectives. It was hypothesized there would be no significant differences in gain scores or perceptions between a group of students taught using PBL in comparison to the group taught using traditional methods. Data analysis indicated statistically significant gain scores in both of the groups with a higher gain score in the PBL group. Data analysis also revealed statistically significant differences in the total score on the SPOCQ in favor of the PBL group. This study found positive effects for well-implemented PBL instruction with these students. However, much more remains to be known. Future research should include longitudinal studies expanded to different subjects, grade levels and populations of students. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]