In many companies, the IT support is not provided by a single system, but rather by a collection of interacting systems. Although the user only interacts through one system, the customer information may be managed by one system, the transaction itself may be managed by another system, authorization by a third system, the tasks to be performed by a fourth system, the financial information by a fifth, and so forth. Hence, managing the requirements of a new feature in such extensive and complex software in an effective way is difficult and pushes the use of the use-case modeling technique. The challenge lies in developing and managing a hierarchical structure of use-case models, as well as establishing traces between the contents of these models. The end user of the complete IT support will experience it as one system, while the actual maintenance and enhancements will be done in several systems. In this tutorial, we will present well-proven techniques and patterns for developing multiple use-case models of large-scale systems, and discuss real-life experiences of developing such systems.