Purpose: The purpose of this study is to examine whether or not a winning performance within professional cycling influences the stock exchange. It looks at the impact a win has on a team’s main sponsor through the effect on said sponsor’s company stock price. Methodology: This study has a positivistic and deductive approach when testing the theory of market efficiency. It uses event study methodology to measure the effect of new information on a company’s stock price. The event period lasts from the last working day before the event to the first working day after the event. The study examined 99 winning performances in the UCI World Tour, from January 1, 2005, to April 30, 2016. Normal return before the event window was calculated from an estimation period of 250 working days. A T-test was used to assess if the results were significant. Results: The study found, based on the complete samples including all cycling races, that there is no significant effect on a main sponsor’s stock price. The Average Abnormal Return came out as 0,04 percent. 46 one day races were examined, resulting in an AAR of -0,1 percent. This means that there was no significant effect on the sponsor’s stock price. For the stage races, on the other hand, the 44 measurements resulted in an AAR of 0,38 percent with a positive 5 percent significance level. Nine measurements derived from the Grand Tours resulted in an AAR of -0,96 percent and a negative 5 percent significance level. Conclusions: The conclusion of this study is that there is no significant effect on the main team sponsor’s stock price, regardless of categorisation. While single day races generated no significant effect, the stage races did have a positive significant effect. Based on the study, The Grand Tour races resulted in a negative effect but the samples for this category were too few to draw a final conclusion from.