Abstract: In this study, we established an efficient Agrobacterium-mediated transgenic system in rice (Oryza sativa L.). During the studies in the japonica (Xiushui-11) and indica rice cultivars (XC-95), the role of various factors responsible for virulence of Agrobacterium was screened more carefully to establish a better transformation system for the rice cultivars. MS and AB media (as VIM) proved to be efficient for Xiushui-11 and XC95, respectively. 100 μM AS (acetosyringone), pH 6.0 (VIM and COM) and use of either sucrose, glucose (Xiushui-11) or sucrose (XC-95) produced the best results for both of japonica and indica rice. Bacterial cell density A₆₀₀ 0.4-0.6 for 10-15 min was the most favorable optimized condition. Completely dark (Xiuishui-11) and light (XC-95) conditions during co-cultivation period were found to be ideal for transformation process. The significance of achieved results has been discussed properly.