Rice farming remains an important undertaking in Asia and Africa due to its important role in maintaining essential food supply. Rice ranks second to maize in providing more than one-fifth of the calories consumed worldwide. In Kenya, rice is an important food crop and cash crop. A survey of 773 farmers was undertaken in Mwea, West Kano, Ahero and Bunyala rice growing regions to investigate the technical efficiency and technology gap ratios. The meta-frontier estimates indicate that the technical efficiency of Mwea, West Kano, Ahero and Bunyala was 0.556, 0.475, 0.402 and 0.45 respectively. The regional efficiencies indicate that the technical efficiency of Mwea, WestKano, Ahero and Bunyala was 0.557, 0.784, 0.833 and 0.937 respectively. Thus, the technology gap ratio was 0.998, 0.605, 0.482 and 0.48 for Mwea, West Kano, Ahero and Bunyala respectively. The results thus suggest that a narrow gap existed between the region and the meta-frontier results for Mwea, while a wider gap existed for West Kano, Ahero and Bunyala implying that Mwea farmers were more technically efficient than farmers in the other schemes. Using the fractional regression models the determinants of efficiency were found to be age, farmer s gender, humidity, rainfall, temperature and adopting technologies. Acknowledgement :