When roughly 94 percent of Fortune 1000 chief executive officers are men, what qualities drive the 6 percent who are women to the most elite reaches of corporate leadership? To find out, Korn Ferry Institute studied 57 women who have been CEO — 38 currently and 19 previously — at Fortune 1000-listed companies and others of similar size. We analyzed structured interviews with all 57 women as well as the results of psychometric assessments taken by two-thirds of them.