In their exploratory study Muniz & O’Guinn (2001) found three markers of a brand community: a sense of belonging, rituals and tradition and a sense of duty toward the community. Two of the three markers of community have been included in conceptual models on brand communities. However, the third marker (sense of duty) has not been implemented up to now. Hence, the objective of this thesis is to extend Bagozzi & Dholakia’s (2006) brand community model by incorporating the construct “sense of duty”. In this research, a conceptual model of brand communities is developed. Overall, the findings support the conceptual model. The results show that sense of duty is a decisive mediator of brand community behaviours and that sense of duty is divided into three distinct components: new member integration, product usage and member retention. Further, this research indicates that community-related behavioural intentions are not significantly related to purchase intentions.