The factors influencing the frequency of rice transformation mediated by Agrobacterium have been investigated by using 16 commercially important indica and japonica rice cultivars or lines. The main results were as following: For most rice CC medium was the best for both callus initiation and subculture. With supplement of 2.5-5 mg/L ABA the quality of calli can be improved. The concentration of selective agent for Indica rice callus was lower than that for japonica rice callus. Agrobacterium tumefaciens strain EHA105 was more efficient than LBA4404 and AGL1 for rice transformation. The inhibitive effect of cefotaxime to Agrobacterium was better than that of carbenicillin. The partial desiccation treatment after co-cultivation was beneficial to inhibit the growth of Agrobacterium and increase transformation efficiency. A stable and efficient Agrobacterium-mediated transformation system has been established in ten different rice cultivars and fertile transgenic plants have been obtained.