We analyze changes in concentration levels in the U.S. Advertising and Marketing Services industry using data from the U.S. Census Bureau’s quinquennial Economic Census and the Service Annual Survey. Heretofore largely ignored, these data allow us to redress some of the measurement problems surrounding estimates found in the existing literature Firm level concentration as measured by the Herfindahl-Hirschman Index varies across the sectors comprising the industry, but all are within the range generally considered as indicative of a competitive industry. At the holding company level, the four largest organizations account for about a quarter of the industry’s total revenue, a share lower by an order of magnitude than that frequently cited in the trade press.