An experiment was conducted during 1997-99 with Roundup Ready® (glyphosate-tolerant) cotton (PM 1244 RR in 1997, PM 1220 RR/BG in 1998 and DP 5415 RR in 1999) grown in conventional-till and no-till production systems and infested with a natural population of perennial johnsongrass and Palmer amaranth. The soil type was silt loam with 1.1 percent organic matter and pH 6.4. The area was not irrigated. A split-plot design with six replications was used. Tillage systems were main-plot treatments consisting of 16, 40-inch-wide rows by 40 feet long. Conventional-till consisted of subsoiling between rows (45 to row direction in 1996) and hipping rows each fall, re-hipping each spring, operating a bed conditioner to reduce bed height and/or destroy vegetation, and in-season cultivation two or three times each year leaving a 12-inch undisturbed band centered on the row. Herbicides applied at planting and in-season were made to a 20-inch-wide band centered on the cotton row. No-till treatments consisted of an initial subsoiling and hipping to establish a bed for planting and reducing the bed to the proper planting height with a bed conditioner in the fall of 1996. There was no further tillage. Herbicides were applied broadcast.