User participations in virtual communities include both information seeking and sharing behaviors to varying degrees. The intentions to share and to seek information may have different motivations. However, existing studies rarely analyze the intentions for both types of behaviors. This study explicates the antecedents of the two types of usage intentions - intentions to share and intentions to seek - using a model that integrates social, community, and individual factors. The model is validated using a survey of 502 online investors of the most popular online stock message board in South Korea. The results show that the sense of belonging, entertainment value, and perceived usefulness influence both the intentions to share and seek. In addition, reputation seeking enhances the intention to post while perceived knowledge reduces the intention to seek.