QoS management has been extensively studied in network-based multimedia applications. However, its application to Web services is very recent. In this paper, we present WS-QoSM, a Web services QoS management architecture capable of supporting at runtime the QoS management operations, QoS provisioning and assurance in delivering Web services. Our proposed architecture is based on the commonly used notion of QoS brokerage service to mediate between service requesters and service providers. Its responsibilities include performance monitoring of Web services, implementation of Web service selection policies, and negotiation of QoS. Besides, we present a server-oriented scheme for load distribution based on the sender-initiated and receiver-initiated strategies previously used in general distributed systems.