MILITARY PSYCHOLOGY, 23:220–236, 2011 Copyright © Taylor & Francis Group, LLC ISSN: 0899-5605 print / 1532-7876 online DOI: 10.1080/08995605.2011.559394 Evaluating the Psychometric and Measurement Characteristics of a Measure of Sexual Orientation Harassment Armando X. Estrada, Tahira M. Probst, Jeremiah Brown, and Maja Graso Department of Psychology, Washington State UniversityVancouver, Vancouver, Washington We use classical test theory (CTT) and item response theory (IRT) methodologies to examine the psychometric and measurement properties of an instrument designed to assess sexual orientation harassment among military personnel (N = 71,989). CTT analyses indicated that items were unidimensional and exhibited adequate levels of reliability. IRT analyses demonstrated that the items functioned similarly and exhib- ited appropriate levels of item discrimination. However, the analyses also suggested that the sensitivity of the items may be limited. Differential test functioning analy- ses provided evidence of the measurement equivalence of the instrument across male and female respondents. The findings provide support for the psychometric proper- ties and measurement equivalence of the instrument for measuring sexual orientation harassment among male and female military personnel. We discuss the implications of our findings for future research on sexual orientation harassment in the workplace. Empirical research on workplace harassment has increased dramatically in the past two decades. Although studies to date have increased our understanding of the nature and prevalence of sexual harassment (U.S. Merit Systems Protection Board [USMSPB], 1988, 1995) and ethnic harassment (Scarville, Button, Edwards, Lancaster, & Elig, 1999; Schneider, Hitlan, & Radhakrishnan, 2000), research The views expressed in this article are those of the author(s) and do not necessarily reflect the official policy or position of the Department of Defense, the U.S. government, or any of its agencies. Correspondence should be addressed to Armando X. Estrada, WSUV Psychology Department, 14204 NE Salmon Creek Ave., Vancouver, WA 98686-9600. E-mail: aestrada1@vancouver.wsu.edu