Master's Thesis from the year 2012 in the subject Communications - Public Relations, Advertising, Marketing, Social Media, grade: 1,3, University of Siegen (Fakultät III), language: English, abstract: Primarily, a review on theoretical foundations and the history of Viral Marketing is shown. Based on this a variety of different definitions were analysed to set up a practical definition for this thesis. Thereafter, possible targets of Viral Marketing are illustrated, followed by necessary elements of Viral Marketing campaigns, and finally by an approach to measure the effectiveness. By means of an online questionnaire, a survey was conducted to collect empirical data from which to analyse Viral Marketing within social networking sites and detect useful information for the practical use of Viral Marketing. The results of the analysis show the accelerating influence of social networking sites and other factors regarding the effectiveness of Viral Marketing. In addition, specific characteristics which make Viral Marketing messages appealing, as well as the preferred types of Viral Marketing messages are illustrated and should help to understand how to create and design an effective Viral Marketing Campaign.