IRTEQ: Windows Application that Implements IRT Scaling and Equating. Maintaining comparability of scores from different forms of a test (and/or from different test administrations) has been a major technical challenge for psychometricians. Today with a major focus of state testing programs on the assessment of growth, the challenge of maintaining comparability of scores has become even more important. Over the years, several IRT based scaling/equating methods have been developed to provide solutions (e.g., Hambleton, Swaminathan, & Rogers, 1991; Kolen & Brennan, 2004; Lord, 1980). While equating methods research has flourished because of the need for technically sound designs and analyses, software development has been limited. The major testing companies of course have the software they need for scaling and equating but software available for researchers and graduate students is very limited. And, the few computer programs for test scaling and equating that have been developed for wide use, do not always include features of special interest to researchers. For example, available software cannot handle all the popular IRT models being applied to test data, and cannot handle some of the popular equating designs. Thus, a demand for a computer program that is more generalized and powerful for various uses in research and test development has grown in the field, and as a result, a Window application, called IRTEQ, was developed to address that need.