Member-initiated virtual communities for product knowledge sharing and commerce purposes are proliferating as useful alternatives to company information and commerce Web sites. Although such communities are easy to create with the availability of numerous tools, the challenge lies in keeping the community alive and thriving. Key to sustainability is members' Sense Of Virtual Community (SOVC) so that they feel responsible for contributing their knowledge and creating value for others. However, it is unclear what leads to the SOVC among knowledge contributors. Building on appraisal theory, we hypothesize that the fulfillment of contributors' informational, instrumental, entertainment, self-discovery, and social enhancement needs will increase their SOVC. To test the hypotheses, we surveyed knowledge contributors in a beauty-product-related community to examine the relationship between their needs' fulfillment and SOVC levels. Other than the social enhancement need, all other needs' fulfillment were found to be positively related to SOVC levels. To further understand how the SOVC of knowledge contributors changes over time, we conducted a longitudinal analysis of a panel of these members. We discovered that over time, changes in the perceived fulfillment of their instrumental, entertainment, and self-discovery needs determined the change of their SOVC. The results have implications for future research as well as for the sustainability and value generation from such virtual communities.