The analysis of a scenario specification for a new system can address some questions of system performance, in the sense of delay and capacity estimation. To assist the analyst, a performance model can be generated automatically from a Use Case Map specification in the UCM Navigator (UCMN_AV). This paper describes the process, and the information that must be supplied in the way of scenario annotations. It illustrates the tool-supported process with a substantial example related to electronic commerce, which demonstrates the impact of provisioning the software architecture for concurrency.