When glyphosate, sethoxydim, and organic arsenicals (MSMA in 1982 and DSMA in 1983 and 1984) were applied as postemergence treatments for three consecutive years to field plots for the control of johnsongrass in cotton, repeated annual applications of sethoxydim were more successful than other herbicides in protecting yields of cotton and reducing populations of johnsongrass with time. After the first year of treatment with sethoxydim in 1982, when cotton maturity was delayed and an 18% loss of cotton occurred, populations of johnsongrass were reduced to the extent that they were no longer a threat to yields in plots treated with sethoxydim in 1983 and 1984. Although DSMA and glyphosate reduced yield losses when compared to cultivated control treatments, substantial yield losses occurred every year and populations of johnsongrass remained unchanged after 3 years of treatment. Averaged over 3 years, plots treated with sethoxydim produced 94% as much cotton as weed-free plots, as compared to 60 and 45% for plots treated with glyphosate and MSMA/DSMA, respectively. Cultivated control plots produced only 13% as much cotton as weed-free plots.