We analyze a priority queueing system with congestion control based on thresholds. A priority queue with a triple of thresholds consisting of an abatement threshold, an onset threshold and a discard threshold was investigated by San-qi Li. We extend Li's model to a priority queue with N triples of thresholds and obtain the stationary probabilities of queue length by using the Embedded Markov chain method. We obtain the loss probability and the mean delay of packet of each class. We apply our result to signaling system no. 7 network with a congestion control based on thresholds. (C) 2000 Elsevier Science B.V. All rights reserved.