Relationship marketing is conveniently thought of as a means of building forms of customer loyalty which transcend preferences for particular products. This implies a conceptual divorce between the customer-supplier relationship and the process of product design. This paper examines the interaction between the two. It describes, through a case study of a small software company, how a participative methodology by suppliers to involve users in the design of new products and product development can be instrumental in developing and maintaining effective marketing relationships. The conclusions focus on the activities that may be used to implement the aims of relationship marketing, through the use of designer-managed user groups.