The Intelligent Network (IN) is an telecommunications services architecture which enables the rapid creation and deployment of supplementary telecommunications services. However, this flexibility makes the management of the network performance critical in ensuring that customers receive their expected Quality of Service. This thesis describes a model which has been developed to predict the delays in the network due to IN-specific service processing. The model proposed is a queuing network which builds on the existing state of the art as follows. The characteristics of the flows between the IN physical entities are considered and general service time distributions are assumed at each entity. Additionally, the model allows the reservation of capacities as the SCP for each service type. An analytic formulation was developed using the decomposition approximate method. The model was also simulated in order to ascertain its’ accuracy. The results of the analytic solution and the simulation were compared for different scenarios and the results are presented in this thesis. The analytic approximation was found to be a very good solution for situations where network utilisation was low or medium. As the utilisation of the network increases to higher utilisation factors, the accuracy of the analytic solution decreases.