A field investigation was carried out for six seasons from kharif 2006 through kharif 2009 at Agricultural Research Station, Kathalagere, district Davangere in the southern transitional zone of Karnataka. The present investigation was taken up to know the bioeffectiveness of azimsulfuron 50 DF in comparison with butachlor, 2,4-DEE, hand weeding for weed control in transplanted rice. The field experiment was laidout in randomized block design with 8 treatments viz., T1: Azimsulfuron 50 DF @ 27.5 g a.i./ha + 0.2% Surfactant, T2: Azimsulfuron 50 DF @ 30.0 g a.i./ha + 0.2% Surfactant, T3: Azimsulfuron 50 DF @ 35.0 g a.i./ha + 0.2% Surfactant, T4: T2 + 1 hand weeding @ 40 DAT, T5: Butachlor 50 EC @ 1.25 kg a.i./ha (standard check), T6: 2,4-DEE 2.0 kg a.i./ha (4 WAT), T7: Hand weeding twice (20 and 40 DAT) and T8: Weedy check. The treatments were replicated thrice. Azimsulfuron 30.0 g a.i./ha (19 DAT) + 0.2 % Surfactant followed by one hand weeding at 40 DAT recorded significantly lower total weed density (0.00-1.67/ 0.25 m2) and total weed dry weight (0.00-0.26 g/ 0.25 m2) than all the herbicidal treatments and was at par or better than hand weeding twice during 2008 and 2009; resulting in highest grain yield (6834, 6683 and 6102 kg/ha in summer 2008, kharif 2008 and kharif 2009, respectively) and straw yield (7008, 7030 and 6494 kg/ha in summer 2008, kharif 2008 and kharif 2009, respectively) of rice. During summer/ kharif 2007, azimsulfuron 35 g a.i./ha was provided the maximum control of weeds with maximum yields among the herbicidal treatment, while during kharif 2006, maximum grain and straw yields were observed to be under butachlor 1.25 kg a.i./ha.