The research reported in this paper was conducted at the Conchal county in Sao Paulo State, Brazil, in a Red Yellow Latosol with 1.75% of organic matter, with the objective of studyin g the effect of continuous use of selected herbicides on the weed control on a 'Pena' Citrus sinensis (L.) Osbeck citrus orchard, graf ted on 'Limão-Cravo' (Citrus Limonia Osbeck). Kandon blocks experimental design with 12 treatments and 4 replicates was used. The treatments and herbicide application rates (kg/ha) were : terbacil at 3.2 sima zine at 4.0; ametryne + secbumetone at 4,5; dichlobeni l at 5.0; diuron at 3,2; bromacil at 3.2; bromacil at 3.2; bromacil + diuron at 3.2; paraqua t at 0.6; glyphosate at 1.61 and MSMA at 1.77 , and two cont rol plots manually til led, one year ly and the other whenever weeds covered 25% of the plot. The orchard was planted in may 1975, and the first herbicide application was done in october 1977. The area of each plot was 54 m2 (3.0 x 18.0 m) with 4 plants per plot. The last herbicide application was done in 1982. The effect of the treatments on weed control was evaluated through species couting and also visually. The herbicides used showed control ranging from acceptable to excellent, depending on the specific weed composition in the plot. The herbicides with best weed cont rol index as well as longer residual effects were bromacil + diuron, diuron bromacil, ametryne + secbumetone and terbacil. Among the post-emergency her bicides the best indexes were obtained with glyphosa te and paraquat.