Integrity is a critically important individual differences construct and plays a central role in organizational sciences. Integrity tests have a long-standing history in the field of personality assessment. In this chapter, we review four different conceptualizations of how integrity test scores map into the personality domain as described by the widely used Big Five framework of personality traits. Integrity test scores have been conceptualized to reflect: (1) the Big Five factor of Conscientiousness or one of its facets; (2) a distinct sixth factor -Honesty-humility - of personality separate from the Big Five; (3) a composite, formative variable made up of several subfacets from different Big Five factors; and (4) a latent super factor that underlies three of the Big Five factors. We present a summary of the theoretical arguments for each conceptualization and the empirical evidence in support of them. Theoretical and empirically based arguments support the fourth conceptualization. We also review some measurement issues and recent controversies involving trustworthiness of test publisher data.