Managing long-term sustainable customer relationships is of concern to many organisations today. A successful relationship marketing (RM) strategy requires an understanding of the constituent constructs as well as the interrelationships between these constructs. Relationship desire, relational benefits, relationship satisfaction and relationship strength were the four RM themes of interest in this research. Furthermore, this study extends previous research by identifying salient interrelationships between these four RM themes and their impact upon retention intentions within a high involvement, high-credence, non-profit service context. Key findings of this study included that: 1) customers’ desire for a relationship influences their perceptions of relational benefits and relationship satisfaction; 2) relational benefits impact upon relationship strength and relationship satisfaction; and 3) relationship satisfaction is the primary influencer of relationship-based retention intentions. The major implication of this study is that not all RM themes directly influence a customer’s decision to remain with a service provider. Overall, the research expands extant RM theory and provides useful practical contributions.