The problems of analysing genetic resources data are reviewed, with particular reference to the use of graph-theoretic methods and to the concept of “validation”. A taxonomically difficult set of Stylosanthes (Leguminosae) accessions is subjected to classification, a minimum spanning tree, and a two-neighbour network. It is then subjected to a novel multiple-nearest-neighbour approach (program NEBALL) which provides a more detailed and exact summary of the configuration; this is validated by appeal to phytochemical, provenance and performance data. The results suggest that, providing the assumptions implicit in the model are met, the new technique may well be the most powerful yet available for the study of genetic resources data.
