The nature and quality of a firm's dialogue with its customers is a core capability. Few firms are able to manage this dialogue effectively and use what they know to add more value for customers and ultimately improve firm performance. Knowledge management (KM) functions are therefore being asked how their expertise can help companies do a better job in this area. This paper examines the wide variety of ways organizations use KM in their customer relationships. It begins with an examination of the need for Customer Knowledge Management (CKM) and how it differs from Customer Relationship Management (CRM). It then looks at the four different dimensions of customer knowledge and at some of the innovative ways companies use them to add value for their customers. It next discusses the key organizational challenges of implementing CKM. The paper concludes with some best practices and advice about how to implement a program of CKM successfully in an organization. It suggests that CKM is not a tool like CRM but a process that is designed to dynamically capture, create and integrate knowledge about and for customers.