Cognitive flexibility (CF) is a neuropsychological construct that has recently seen increased interest in the research literature. With implications that span a range of scientific specialties, the construct has been studied utilizing a broad variety of measurement modalities. While the Wisconsin Card Sorting (WCST) test has been identified as the gold standard measure for studying CF, for a variety of reasons competing techniques have been applied each purportedly measuring the same underlying construct. In a clinical sample of 119 adult neuropsychological testing patients, performance on the Delis Kaplan Executive Functioning System Color-Word Interference test and the Trails-B test was compared to the WCST. A factor analysis of scores indicated a three factor solution with the WCST standing independent of performance on the other two measures. These results indicate that the three competing approaches cannot be used independently to measure CF.