The world collection of Centrosema brasilianum (L.) Benth. germplasm comprises, at present, approximately 200 accessions. Most have been collected in Brazil and Venezuela during collecting missions carried out by CIAT between 1975 and 1986 in collaboration with national research institutions. Germplasm collection sites extend between l6°S and 10°N, and between 35°W and 80°W. They are concentrated in NE Brazil and NE Venezuela. 82% of the collection originates from semi-dry and subhumid environments (370-1680 mm rainfall year-1). The remaining 18% were collected in the humid tropics (1710-2920 mm yr-1). Soils at collection sites are generally acid and of low fertility. In a preliminary evaluation trial conducted with 130 accessions at Quilichao, Cauca, Colombia, considerable variation was found in herbage yields which were affected by plant adaptation to soil acidity with high Al and Mn levels (pH 4.1, 89% Al saturation and 110 ppm Mn) and by susceptibility to Rhizoctonia foliar blight (RFB). Accessions were grouped into 10 clusters, the highest yielding of which comprised eight accessions with high tolerance to RFB. Contents of crude protein, P and Ca were also variable but within a range considered normal for Centrosema. Another highly variable character was the earliness of flowering. No clear association was found between germplasm performance in the preliminary evaluation trial and rainfall conditions at collection sites. The need to collect more germplasm of C. brasilianum is discussed and several regions for further collections are identified.