This study explores five years of data from Red Books (Standard Directory of Advertising Agencies), a respected advertising industry database. Specifically, it explores the gendered composition of advertising creative departments across the globe, and is framed by sociological models of gender segregation and creative systems theory. The study demonstrates pervasive and systemic horizontal and vertical gender segregation within advertising creative departments worldwide. Using frequency test and correlation analysis, the authors analyzed 23,746 personnel data points from 4,713 agencies, in 50 countries, across five regions, from 2012 through 2016. In the process, they quantified the significant underrepresentation of women in advertising creative departments. The study demonstrates a global average of only 23.5% women working within advertising creative departments, while revealing an average of just 16.1% women within creative management. Detailed analysis by five geographic regions and by country is also presented. Finally, trend analyses predict a modest increase in women in advertising creative departments in 2017 and 2018, though not on a scale that would indicate systemic change.