With the emergence of Web 2.0 technologies such as BBS, blog, microblog, and social networking services, people are not only exchanging information online but also expressing ideas by virtue of user-generated content (UGC). The amount of UGC available is already voluminous and continues to grow on a daily basis. UGC is not regulated by top-down rules, allowing users free to decide what to write about (topics), how to write (expression style), and when to post (publishing time). Since UGC is produced without supervision, standards and conventions, the effect of UGC, especially the extreme negative UGC or unusually positive UGC, on enterprises is largely unknown. The uncertainties that arise from organizations’ management of UGC include the following four aspects. The first one is the uncertain quality of UGC usage data. Due to the unpredictability of UGC’s publishing, the complex interaction between the endless UGC, the statistics of UGC involves a lot of uncertainties, such as how to determine the best time to collect UGC, how to define the right boundary to gather UGC, and how to draw representative samples to descript UGC, etc. The second one is the uncertain credibility of UGC. After the organization obtains the UGC through the first step, to classify the huge amount of UGC into credible and incredible ones becomes essential for any decision that must be made based on reliable data. However, the identity of UGC’s creator, the intention of UGC’s publishing, and the semantic contained in UGC are not easy to judge, which sets barriers for distinguish credible UGC between incredible UGC. The third one is the uncertain mutual influence between UGC and whom? Social network platforms are becoming an important information gathering tools, where new people meet and new friends share their interests and opinions. Anyone is connected with others and is influenced by others. The world is becoming more and more flat, but it is not absolute equal. On the other hand, the organizations will take actions to deal with UGC. Thus, for Internet users, to follow UGC or to follow the information from organizations depends on the tug-of-war contest between UGC and the information from organizations. The fourth one is the uncertain effect of organizations’ intervention in UGC. On the one hand, social media has been recognized as an important catalyst for various unexpected events. One the other hand, social media provides new techniques to manage unexpected events. The rich user generated contents (UGC) and clear social relationships among social media users provide rich sources for forecasting, monitoring and evaluating unexpected events. But, how to manage UGC to promote the management of unexpected events is still a challenging problem. The aim of this workshop is to engage multidisciplinary discussions with novel ideas and applications geared towards uncertainties research on UGC.