Two rice (Oryza sativa subsp. japonica cv. Nipponbare) ribosome recycling factor genes--OsfrrA and OsfrrB had been identified and characterized in this study. The gene OsfrrA is located on chromosome 4 while OsfrrB on chromosome 7. No other homologue is found in rice organelle genomes. Both genes are unique in rice genome and constitutively expressed. The N-terminal character of their encoded protein products suggests that the proteins are transferred to mitochondrion and chloroplast respectively and carry out their functions. The sequence conservation and the constitutive expression profile of the two genes strongly imply their indispensable role in plant growth. In addition, these sequences share phylogenetic homology to some extent with other prokaryotic and eukaryotic RRFs, providing further evidence for the endosymbiotic theory, and implying the potential value of RRFs in molecular evolution research.