The nucleotide sequence of a 27,588-bp region of rice mitochondrial DNA was determined. This sequence contains putative genes that encode initiator methionine tRNA (trnfM), subunits III (nad3) and IV (nad4) of the NADH dehydrogenase complex, and ribosomal proteins S3 (rps3), S12 (rps12) and L16 (rpl16). An open reading frame that contains sequences homologous to parts of rps2 and atpA is also present. In addition to these regions, there are many short sequences with homology to fragments of mitochondrial DNAs from rice or other plants. These sequences may be remnants of multiple rearrangements of the genome and their presence seems to explain, in part, the large sizes of the mitochondrial genomes of higher plants.