Industrial systems are examples of complex and often long-lived systems in which software is playing an increasingly important role. Their architectures play a crucial role in maintaining the properties of such systems during their entire life cycle. In this paper, we present the results of a case study based on a series of interviews and a workshop with key personnel from research and development groups of successful international companies in their Swedish locations. The main goal of the investigation was to find the significant factors which influence system and software architectures and to find similarities and differences between the architecture-determining decisions and the architectures of these systems. The role of the architect was an important subject of the investigation. Our findings result in recommendations relating to the design and evolution of system architectures and suggestions regarding areas in which future research would be beneficial.