Oryza longistaminata, a perennial wild rice species with an AA genome, is characterized by the presence of rhizomatous stems. The rhizomatous trait in rice was previously shown to be quantitatively controlled by many genes, but the molecular mechanism related to rhizome development is still unknown. In the present study, expressed sequence tags (ESTs) generated from rhizome tips of O. longistaminata were collected and analyzed. A total of 10,283 complimentary deoxyribunucleic acid clones were randomly sequenced, which generated 10,136 raw sequences, and finally, 4,419 unisequences with diverse functional categories were generated. These unisequences were mapped onto the Oryza sativa genome, which revealed that 4,285 (96.97%) and 4,151 (93.94%) of the unisequences were alignable to the japonica and indica genomic sequences, respectively, with >80% sequence identity. Additionally, 41 unisequences showed four typical types of alternative splicing patterns. More than 600 simple sequence repeats were identified in these unisequences. A subset of unisequences were physically colocalized onto rhizome-related quantitative trait locus intervals in rice and sorghum, and one gene, OLRR1, was further confirmed to be enriched in the rhizome tip and young leaf by real-time polymerase chain reaction and in situ hybridization. Unisequences reported in this study provide valuable data for molecular dissection of the rhizomatous growth habit in O. longistaminata.