The purpose of this study was to assess and describe the status of program evaluation within the National Science Foundation's (NSF) Research Experiences for Undergraduates (REU) sites. The National Science Foundation's REU program supports thousands of undergraduates annually in hands-on, immersive research experiences under the mentorship of science professionals. To date, there is a lack of published or accessible evaluation results from these REU programs and it is unknown what evaluation approaches are being used in the REU programs, how they are designed and implemented, how evaluation findings are utilized, and what barriers to evaluation activities exist. A self-administered electronic survey consisting of a combination of closed- and open-ended answer questions was utilized for data collection. A total of 343 surveys were started with some attrition throughout the survey, with 276 completing the survey. Frequencies of responses were employed to address the research questions. Open-ended responses were inductively coded and once coded, the data were quantified and integrated into the other quantitative data from the remaining survey items. The majority of respondents were academic institutions of higher education running in-person REU programs over the summer for cohorts of 8-12 students. Nearly all REU sites reported that they evaluate their programs and collect student data, while about half also collect mentor evaluation data. A majority of REU sites employ multiple student evaluation data collection strategies, with pre-and post-surveys the most frequent. This study provides a summary overview of the evaluation practices of REU sites, including the methods utilized, stakeholders involved, targeted outcomes, and utilization of evaluation results to inform program design, while also identifying barriers hindering effective evaluation and improvement efforts. [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.]