Membership programs are widely-used marketing tools. Many customers belong to a number of different membership programs across a variety of organizations and contexts. Memberships are based on the idea of mutual benefits of a relationship. Memberships in general offer tangible and intangible benefits such as free admission, discounts, special offers or access to special services, and a sense of belonging and identity. General organizational benefits of memberships besides customers are funding, fee revenue, legitimacy, and various kinds of member support. Memberships are used as competitive relationship marketing tools to retain customers, build relationships and encourage member participation. Many memberships have developed from merely being reward programs into an attempt to create emotional bonds based on calculative and affective commitment. Research into memberships is an emergent multidisciplinary field of interest for practitioners and scholars representing different disciplines. This thesis is delimited to study members and memberships at nonprofit organizations within tourism settings from a relationship marketing perspective. The aim is to get insight into why individuals choose to become members, why they stay on as members, and how members interact and use their memberships. The overall objective is therefore to explore motivations related to memberships and how this is reflected in different member behaviours and member roles within tourism settings. Throughout this thesis a mixed-method research approach was applied combining qualitative and quantitative research to explore the membership phenomenon. This thesis is comprised of four studies based on data from an explorative pre-study (12 respondents), a questionnaire survey (755 respondents), and a Nordic cross-case study (37 respondents). Findings showed member motivations, behaviours and roles within the tourism system. Member motivations were identified as altruistic (doing good for others), self-interest (doing good for yourself) and social (doing good with others). Findings further showed member interactions with other members (M2M), customers/visitors (M2C) and supported organizations (M2B). Member behaviours found were: returning (retention); supporting, visiting, using member information (participation); marketing, spreading WOM and recruiting new members; and volunteering (co-creation). Furthermore, significant relations were found between motivational dimensions, behaviours and member demographics (age, gender, and distance). Members performed multiple overlapping roles from being supporters and visitors to front-line co-creators