Advances in social virtual worlds, such as Second Life, create new opportunities for various applications in business, education, entertainment, and many other real-world domains. However, the benefits of social virtual worlds cannot be realized without sufficient user participation. There is thus far a paucity of research that has investigated people's motivations for participating in social virtual worlds. Motivated by such concerns, this study aims at investigating the motivations for participating in social virtual worlds based on the uses and gratifications theory. An online survey with open-ended questions is conducted to identify the key motivations of user participation in Second Life. Content analysis is used to code and categorize the responses from 188 subjects. The results show that users' motivations or needs for participating in Second Life can be categorized into three types, namely, utilitarian needs, hedonic needs, and social needs. This research has important implications for both researchers and practitioners. © 2010 IEEE.