Research on organizational diversity, heterogeneity, and related concepts has proliferated in the past decade, but few consistent findings have emerged. We argue that the construct of diversity requires closer examination. We describe three distinctive types of diversity: separation, variety, and disparity. Failure to recognize the meaning, maximum shape, and assumptions underlying each type has held back theory development and yielded ambiguous research conclusions. We present guidelines for conceptualization, measurement, and theory testing, highlighting the special case of demographic diversity.