Although Web service technology allows the development and execution of distributed applications, it still lacks facilities to deal with Quality of Service (QoS). Consumers may require services with particular nonfunctional characteristics and expect quality level guarantees. The goal of this paper is to propose an extended Web service architecture supporting QoS management for Web services. It includes brokers to facilitate service selection according to functional and non-functional requirements and monitors to verify QoS attributes. The main contributions of this approach are the use of the Web Services Policy Framework (WS-Policy) standard to enhance the service specification with QoS policies and an extension to the Universal Description Discovery & Integration (UDDI) standard for QoS-enriched Web service publication and discovery.