Field experiments were conducted at Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai to evaluate herbicide bispyribac-sodium in transplanted rice varieties ‘ASD 16’ and ‘ADT 37’ during 2010 and 2011. Seven treatments were included in a randomized block design and replicated four times. The treatments consisted of pre–emergence application of butachlor 500 g/ha, post-emergence application of bispyribac-sodium 10 SC at 25, 35 and 50 g/ha , weed free, hand weeding twice and unweeded check. The results revealed that total weed population and dry weight under bispyribac-sodium at 25 g/ha were at par with the higher doses of bispyribac-sodium at 35 and 50 g/ha during both the years of study. The weed control efficiency and weed index under bispyribac-sodium at lower dose were also comparable with that of higher doses indicating the sufficiency of bispyribac-sodium at 25 g/ha for effective weed management in transplanted rice. The effect of bispyribac-sodium at 25 g/ha on producing tillers and panicles was also at par with that of higher doses and twice hand weeding and significantly superior than butachlor application. Post-emergence application of bispyribac-sodium at 25 g/ha recorded a grain yield of 6.84 and 6.51 t/ha during 2010 and 2011, respectively which were at par with higher doses of bispyribac-sodium, twice hand weeding and weed free and significantly higher than butachlor application. Higher net income and benefit-cost ratio were also associated with the application of bispyribac-sodium at 25 g/ha.