RFLPs of 192 accessions of A-genome rice species were analyzed. One plant was used to represent each accession assayed. RFLPs were detected for the combinations of Dra I-digested total DNA and twenty-one single-copy genomic clones. A dendrogram was constructed using the UPGMA method from a genetic distance matrix. Classification of the A-genome rice species based on RFLP analysis matched well with the conventional classfication. The African annual species, O. glaberrima and O. barthii, were not clearly differentiated by RFLP loci while the Asian species, O. sativa, O. rufipogon and O. nivara, formed a complex wherein none of the species can easily be distinguished from each other. An Asian sub-group that is clearly differentiated from other Asian A-genome germplasm was identified. This consists of some O. rufipogon accessions that did not cluster with the cultivated rice but formed loosely knit groups. Some accessions of O. rufipogon were closely aligned to Indica rice cultivars while the others, mainly from China, were closely aligned with Japonica cultivars. Most of O. glumaepatula accessions from Latin America formed a group which was more closely related to O. glaberrima and O. barthii than other species. Two accessions of O. glumaepatula, however, were aligned with Indica cultivars of Asia. It is possible that the A-genome wild rices in Latin America are of two types. O. rufipogon from the Sepik river of Papua New Guinea was the only material which had RFLP fragments found only in O. meridionails.