The Oxford Forestry Institute has now completed rangewide seed collections of Gliricidia sepium for the establishment of an international provenance trial. Basic biological information on taxonomy, distribution, ecological amplitude, phenology, breeding systems and patterns of variation is presented. The sampling strategy is described highlighting human interference as a major factor distinguishing Gliricidia from traditional forest tree seed collections. Site details are provided for the 30 provenances sampled and a detailed distribution map showing provenance localities is included. The sampling strategy, coordinated evaluation and possible genetic improvement of Gliricidia are discussed in relation to the perceived potential and limitations of the species in tropical production systems.