Although e-services have been recognized for their contribution to strengthening customer relationships and fostering customer loyalty, prior research is heavily skewed toward the field of business-to-consumer interactions and online retail channels. This article explores the evolution of e-services in the business-to-business domain. Based on the case study of ETA SA, a Swiss manufacturer of watch movements and components, it identifies three stages of increasing electronic interaction with customers. The company pioneered online ordering of watch spare parts based on a first generation e-commerce solution and subsequently introduced a comprehensive customer service portal. Our research suggests that moving from the e-commerce solution to the customer process portal involved a significant extension of the e-service portfolio (service innovation), whereas the subsequent stage introduced an additional electronic channel (channel innovation). Every stage in this evolution path forces companies to substantially re-architect their interorganizational process and system linkages. From the experiences of ETA SA, we conclude that a service-oriented multichannel architecture makes it easier to cope with the growing number of e-services and the complexity of serving multiple electronic channels.