Software systems no longer evolve as separate entities but are also integrated with each other. The purpose of integrating software systems can be to increase user-value or to decrease maintenance costs. Different approaches, one of which is software architectural analysis, can be used in the process of integration planning and design. This paper presents a case study in which three software systems were to be integrated. We show how architectural reasoning was used to design and compare integration alternatives. In particular, four different levels of the integration were discussed (interoperation, a so-called Enterprise Application Integration, an integration based on a common data model, and a full integration). We also show how cost, time to delivery and maintainability of the integrated solution were estimated. On the basis of the case study, we analyze the advantages and limits of the architectural approach as such and conclude by outlining directions for future research: how to incorporate analysis of cost, time to delivery, and risk in architectural analysis, and how to make architectural analysis more suitable for comparing many aspects of many alternatives during development. Finally we outline the limitations of architectural analysis.