A putative MADS box gene (RgMADS1) was cloned by screening a rice genomic library with a heterogeneous MADS box probe derived from Antirrhinum majus squamosa gene. Sequencing and Southern analysis showed that RgMADS1 contains a highly conserved MADS box sequence, - whereas the rice genome contains numbers of MADS box genes. A chimera gene of RgMADS1 under the control of CaMV 35S promoter was constructed and used to transform Arabidopsis. Some transformants exhibited abnormal phenotypes in their flowers, which were reflected in the floral structure, number and setting position. Therefore, RgMADS1 is likely a member of rice MADS box gene family and may be involved in the floral establishment and function control in the rice developmental process.