The efficiency of cotton production has been materially increased since 1949 through the use of several pre- and post-emergence herbicides. In the high-rainfall areas, combinations of a pre-emergence herbicide such as isopropyl N–(3–chlorophenyl)carbamate (CIPC) or 3–(3,4–dichlorophenyl)–1,1–dimethylurea (diuron) with one of several post-emergence oils have given more dependable control than the use of single herbicides. In the irrigated areas, early-season weeds have been less of a problem and more attention has been given to herbicides for the control of late-appearing grasses and vines. The substituted ureas, 3–(p–chlorophenyl)–1,1–dimethylurea (monuron) and diuron, have been the most successful herbicides for this use.