Annual morningglory species account for 16% of the cotton yield losses attributed to weeds in the U.S. Directed postemergence herbicides have proven most effective for long season control of these troublesome species. Preemergence herbicides can improve control achieved with directed postemergence herbicides by suppressing early morningglory growth and allowing a height differential to develop between the cotton and morningglory. In studies designed to measure effectiveness of preemergence herbicides for controlling and suppressing early season annual morningglory in cotton, mixture of norflurazon and prometryn proved to very effective with no phytotoxicity to cotton. Tankmixes of norflurazon at 0.56 - 1.34 kg/ha plus prometryn at 0.9 kg/ha increased efficacy on morningglory over either herbicide alone. This tankmix combination offered more flexibility in directed postemergence applications by allowing more time for a height differential to develop between the crop and the weeds. This tankmix also broadened the weed spectrum controlled over either herbicide alone.