Multimedia applications require certain guarantees from the underlying system concerning quality of various parameters, such as the throughput, delay, loss rate etc. We assume that such quality of service (QoS) parameters are normally agreed upon for the duration of a session, and should be maintained throughout that session. If a QoS violation occurs, possibly due to the temporary overload of one of the system components, either the user will notice this and may request a renegotiation of the quality and cost parameters, or the system will automatically do some internal reconfiguration in order to recover from the problem. In the latter case, the system needs to continuously monitor the relevant performance parameters. In this thesis, we develop means for performing such monitoring in the context of a News-on-Demand application. We have designed and implemented a distributed QoS monitoring facility that can be used by distributed multimedia applications for QoS monitoring and QoS violation detection. The system consists of a measurement component and an administrative component. The measurement component is responsible for continuously measuring the end-to-end QoS parameters of connections between the server and client application, while the administrative component is responsible for the overall administration of the monitoring system, which includes raising QoS violation notifications if the quality of service is violated.