In one study, twelve treatments consisting of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), 2-chloro-4,6-bis-(ethylamino)-6-isoproplyamino-s-triazine (simazine), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) applied alternately in a program pre- and postemergence to the weeds were evaluated on ten sugar cane plantations. Averaged data indicated that combinations including atrazine outperformed simazine in every instance and diuron was better than monuron on all plantations but one. Diuron was most effective on grasses, e.g., Digitaria spp. whereas atrazine was outstanding against Commelina diffusa Burm. In a second study on the same plantations, the initial treatment of 5 lb/A of atrazine followed by 3 lb/A of diuron gave outstanding weed control on five plantations. Using 3 lb/A of each material applied simultaneously had merit at times but some plantations required only a single application of either material. Net days of weed control obtained by diuron were inversely dependent on the amount of chemical adsorbed by the soil in both studies and total days control appeared to be dependent on ample rainfall in the second.