This paper describes three clustering algorithms for the dendrochronological analysis of extensive tree-ring data sets. These methods have been thoroughly tested on modern data sets with known felling dates and are shown to produce highly reliable results. An application of one of the methods to the analysis of historic data from the roof of St. Hugh's Choir of Lincoln Cathedral is discussed. Furthermore, this example demonstrates how groups formed by these methods should always be examined in the light of any architectural or other evidence that is available. -- AATA