In 1973, the United Kingdom became a full member of the EEC. A controversial move at the time. Leaders of the political parties has over the decades been pressured to renegotiate the membership several times. Finally, the UK prime minister at the time promised to hold a referendum regarding its status as a member of the union in 2016. The stock market performance over the referendum is analysed in this paper. The analysed stock markets in this paper are the UK, French, German and Norwegian markets. The market model is used to find the proper alpha and beta for the various indices compared to the global index. The model includes data from November 2015 to May 2016. Some of the event windows over the event shows abnormal returns, that are concentrated around the event day, but fades away short after and becomes insignificant. This is over all in line with earlier studies in the topic.