One of the leading programming techniques for the development of distributed applications is the use of Web Services (WS). The strong point of WS technology is the definition of an operating environment that can be adopted to execute applications, independently of the original development and deployment platforms. However, whenever performance is an issue, the message overhead resulting from the XML messaging approach and from the software layers introduced to obtain system abstraction should be carefully considered. This paper presents a simulation-based methodology that makes it possible to predict web services-based application performance, even if the execution environment of choice is not available and the application is not completely developed. This methodology can be used as the basis for performance-driven web services development. The proposed methodology is applied to the development of a simple but realistic web service application.