In this work the Service abstraction is extended to support Quality of Service (QoS) attributes and implemented in the Grid QoS Management (G-QoSM) framework. The framework supports three main functions: (1) providing mechanisms for establishing QoS guarantees via Service Level Agreements (SLAs), (2) enabling QoS management on allocated QoS-aware services, and (3) supporting discovery of services based on QoS attributes. The framework relies on each service offering both a "functional" interface and a "management" interface. The functional interface provides attributes on how a service is to be invoked and how it returns results, whereas the management interface is used to provide QoS attributes and performance characteristics associated with a service. The focus of this paper is on implementing a QoS-based service discovery system, which utilises an extended version of the Universal Description, Discovery and Integration (UDDI) registry.