Workflow management systems (WfMSs) have been used to support various types of business processes. As organizations adopt new working models, such as e-commerce, new challenges arise for workflow systems. One such challenge is that of quality of service (QoS) management. QoS management includes mechanisms that specify, compute, monitor, and control the quality of service of the products or services to be delivered. A good management of QoS directly impacts the success of organizations participating in e-commerce activities by better fulfilling customer expectations and achieving customer satisfaction. In this paper we present an implementation of a comprehensive QoS model for workflows we have specified earlier. While the implementation is being carried out for the METEOR workflow management system, the ideas presented here can also be applied to other workflow systems. In this work we describe the components that have been changed, or added, and discuss how they interact to enable the specification, computation, and monitoring of QoS.