Purpose: Preceptors are relied upon to prepare nursing students during their capstone experience as novice, generalist nurses. There is currently no instrument that measures the preceptor's level of preparedness. The purpose of this study was to psychometrically test a 67-item instrument, the Cap-ExPresS developed during a pilot study, which evaluated the level of self-perceived confidence preceptors reported when working with capstone students. Methods: The subject population was clinical nurses working as preceptors for senior-level nursing students during their capstone experience. The sample included 118 preceptors recruited from four hospitals in the Midwest. A cross-sectional multi-center survey design was used to test the instrument for internal consistency reliability and test-retest reliability. Exploratory factor analysis (EFA) was also performed to support construct validity and to reduce the number of items. Correlations and regressions between independent variables and Cap-ExPresS scores measuring preceptor preparedness were explored. This study tested a revised 67-item Cap-ExPresS with this larger more diverse sample, decreasing the scale to 22 items representing preceptor preparedness with subscales of Student-Centeredness, Pedagogic Competence, Clinical Competence, and Nurse Professionalism. Procedure: After IRB approval, hospital contacts forwarded email instructions with a survey link to all their clinical nurses. The survey screened for inclusion: registered nurses providing direct patient care who had precepted or planned to precept a capstone student. Data were collected securely using Research Electronic Data Capture. After EFA and item analyses, participants were invited to take the retest, evaluating test-retest reliability. Future Research: A valid and reliable Cap-ExPresS can be used to identify best practices to increase the preceptor's self-perceived level of preparedness to precept capstone students. The scale can be used to assess the learning needs of preceptors, and to perform interventional studies, longitudinal studies, and randomized controlled trials evaluating the effectiveness of preceptor training and education on confidence to perform preceptor behaviors. [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.]