Experiments were conducted from 1989 through 1991 to determine the effect of MSMA on efficacy of fluometuron, cyanazine, oxyfluorfen, lactofen, methazole, diuron, and linuron applied POST to entireleaf morningglory. In one set of experiments, applications were made at the cotyledon to three-leaf and four- to six-leaf stages of weed growth. In another set of experiments, applications were made at only one growth stage. Cyanazine, MSMA, or cyanazine plus MSMA were the most efficacious treatments, especially when application was delayed until the four- to six-leaf stage. Adding MSMA to all of the herbicides increased control of entireleaf morningglory, with the magnitude of improvement increasing as the application timing was delayed.