This paper describes the system architecture development process in an international ICT company, which is building a comprehensive e-business system for its customers. The implementation includes the integration of data and legacy systems from independent business units and the construction of a uniform web-based customer interface. The research focuses on the creation of ebusiness system architecture and observes that the architecture is not completely designed through rational decisions and trade-offs. Instead, it emerges through somewhat non-deliberate actions obliged by the situation and its constraints, conflicts, compromises, and political decisions. The interview-based qualitative data is analyzed using grounded theory and a general explanation model for the creation of e-business system architecture is introduced. The role of technical system architecture in ebusiness systems development is clarified and e-business specific requirements for development methods are listed and ...