Many distributed algorithms for computing a property :G p in a network :G v of processors have been proposed in the recent literature. This paper describes two such algorithms for computing centres and medians in networks. Both algorithms are provided for synchronous (asynchronous) tree networks and general networks. Lower bounds and optimality of tree-center and tee-median algorithms have been proved. For both these algorithms the message complexity (i.e., the number of messages exchanged) is O(n:9Ie) and the time complexity is O(n), where n is the number of nodes and e is the number of edges in the network. The paper is well written and the algorithms are clearly described. The reviewer recommends this paper for everyone working on distributed algorithms.