User Software Engineering is a methodology, with supporting tools, for the specification, design, and implementation of interactive information systems. With the USE approach, the user interface is formally specified with augmented state transition diagrams, and the operations may be formally specified with preconditions and postconditions. The USE state transition diagrams may be directly executed, with the application development tool RAPID/USE. RAPID/USE and its associated tool RAPSUM create and analyze logging information that is useful for system testing, and for evaluation and modification of the user interface. We briefly describe the USE transition diagrams and the formal specification approach, and show how these tools and techniques aid in the creation of reliable interactive information systems.