The purpose of this study was to investigate whether participation in a school-based science fair affects middle school students' attitudes toward science and interest in science and engineering careers. A quasi-experimental design was used to compare students' pre- and posttest attitudes toward and interest in science. Forty-eight of the 258 participants completed a school-based science fair during the study. In addition, twelve middle school science teachers completed an online survey. Both the Survey of Science Attitudes and Interest I and II (SSAI-I and II) measured students' attitudes toward and interest in science and science and mathematics self-efficacy, asked about classroom inquiry experiences and gathered demographic information. An online survey gathered qualitative data about science teachers' perceptions of school science fairs. The results showed no significant interactions among completion of a science fair project and attitudes toward and interest in science, science and mathematics self-efficacy or gender. There were significant differences at both pre- and posttest in attitudes between the students who did and did not complete a science fair project. All participating teachers believed that participation in science fairs could have a positive effect on students' attitudes and interest, but cited lack of time as a major impediment. There was significant interaction between level of classroom inquiry and attitudes and interest in science; students who reported more experiences had higher scores on these measures. Classroom inquiry also interacted with the effects of a science fair and participants' pre- and posttest attitude scores. Finally, the amount and source of assistance on a science fair project had a significant impact on students' posttest measures. Major limitations which affect the generalization of these findings include the timing of the administration of the pretest, the number of participants in the experimental group and differences in the science fair procedures at the participating schools. Embedded in a curriculum that includes the teaching of inquiry practices, science fairs may play a role in the inspiration of future scientists, but more research needs to be done on the quality of students' experiences, including amount and type of classroom instruction before and during the science fair process. [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.]