Prior academic research studies have examined the practice of ambush marketing from the perspective of sporting event non-participants (e.g., spectators, viewers and general sport consumers).This exploratory study furthers the line of research into ambush marketing by assessing the attitudes of participants in a major sporting event toward the practice of ambush marketing. Specifically, the researchers surveyed a random sampling of runners who participated in the 2005 and the 2008 ING New York City Marathons. In contrast to the findings in prior studies of sporting event non-participants, this study found that survey respondents reported substantially more negative attitudes toward the practice of ambush marketing. This paper contributes to the sponsorship literature by providing implications for managers of participatory-based sporting events seeking to understand the impact and ramifications of ambush marketing.