MicroRNAs (miRNAs) are important regulators in the development of plants and animals. Several hundred have been identified from animals, and about a dozen have been cloned from plants, mainly Arabidopsis thaliana (L.) Heynh. We have identified nine miRNAs in Oryza sativa L., an important food crop that has been sequenced in recent years. The nine miRNAs include miRNA171 and miRNA167, which were also identified in Arabidopsis. These had the typical properties of miRNAs, including short length, an ability to form a stem–loop structure with a flanking genomic sequence and they could be identified by northern blot analyses. In addition, m-fold program and computational analyses indicted that the potential targets of six of the nine miRNAs are four known gene families and two unknown protein families, which comprise 16 unique genes.