This paper reviews empirical research on top management team (TMT) diversity. A number of scholars have concluded that upper echelons findings, in particular in terms of the consequences of TMT heterogeneity, have been inconclusive. This review conducts an in-depth analysis of conceptual and methodological issues related to upper echelons diversity studies and offers some directions for future research. Sixty journal articles, published in ten top international journals over a 22-year period (1984–2005), were analyzed. The results suggest that upper echelons research is increasingly multidisciplinary in nature; however, in-depth inquiries into the antecedents of TMT composition and the multilevel contextual influences on the implications of TMT heterogeneity are still needed. This review finds that clarity about level of analysis, both theoretically and empirically, remains an important issue in the field and thus a multilevel approach is strongly encouraged. Moreover, the complexity of diversity as a theoretical construct needs to be acknowledged and operationalized accordingly in upper echelons studies.