Two experiments were carried out in order to evaluate the effect of the herbicide clomazone applied in preemergence and the mixture clomazone+ametryn in postemergence on weed control and toxicity to sugarcane. Clomazone from 0.96 to 1.2 kg/ha controlled more than 90% of Echinochloa colona, Panicum fasciculatum and Lagascea mollis, but it was necessary to increase the dose to 1.44 kg/ha to obtain a 90% control of Rottboellia cochinchinensis and between 80 and 90% of Phyllanthus niruri and it had no effect on Cyperus rotundus. The postemergent application of clomazone + ametryn from 800 + 1200 g/ha, showed weed control similar or superior to those of the mixtures of 2,4-D+ ametryn and diuron+2,4-D, which are commonly utilized in the region. A temporal whitening of the sugarcane foliage occurred when clomazone was applied in postemergence, but this symptom disappeared 30 and 60 days after the application.