The purpose of my thesis is to analyse viral marketing in the context of commercial communications. The first part describes the changing environment of commercial communications and focuses on new trends such as guerrilla marketing, event marketing, product placement and use of high-tech. Also, the social media emerged, such as social networks, blogs, multimedia sharing platforms etc. The second chapter deals with the viral marketing theory, its inception and main advantages and disadvantages. At the same time the paper offers the strategy for viral campaign creation, it focuses on viral principles on Facebook, Twitter, and video sharing. The third chapter examines 3 Czech viral campaigns from Aquila, T-Mobile and Fernet Stock. The work is...