An experiment was carried out in the wet season, July - November 1981, to find out the comparative efficiency of Butachlor, Thiobencarb, Propanil and Nitrofen and their effective concentration for the control of weeds in transplanted paddy. Fimbristylis miliacea (L.) Vahl was the major weed and other weeds were Echinochloa colona (L.) Link., Cynodon dactylon (L.) Pers., Oldenlandia corymbosa L., Rotala indica (Willd.) Koehne, Alternanthera sessilis (L.) DC., Hydrolea zeylanica (L.) Vahl, Ammania baccifera L., Sesbania bispinosa Steud. ex Wight, Eriocaulon sieboldianum Sieb. and Zucc. and species of Scirpus. Butachlor, Thiobencarb, Propanil and Nitrofen at 2.0 - 4.0 kg a.i. ha-1 alone or Butachlor and Thiobencarb in combination with Propanil at 1.0 - 2.0 kg a.i. ha-1, as well as two hand-weedings, reduced dry matter of weeds significantly over the unweeded control. Pre-emergence application of Thiobencarb followed by post-emergence application of Propanil, each at 1.0 kg a.i. ha-1, increased grain yield by 37.2% and reduced the dry matter of weeds by 88.8% over the unweeded control.