Thirty Second Life^TM residents were interviewed about their perceptions of the boundary between their virtual world and material world identities and the practices they used to share or to conceal identity information across that boundary. A range of stances toward the boundary – from completely open to completely closed – was found, although even the people who were the most open kept some kind of boundary. Stances toward the boundary and choices about sharing information were related to two broad motivations – relationship formation and reputation maintenance. The interview data is discussed in terms of social penetration theory, social identity theory, theories of stigma, theories of the self and theories of ­anonymity. Ethical issues in virtual world research are also addressed. Suggestions for future research on identity in virtual environments, for the design of virtual environments, and implications for modern conceptualizations of the self are discussed.