Field were surveyed in the two major cotton producing counties in South Carolina for yield loss due to weeds. Areas were located with specific weed infestations and boll were used for comparison. Three counts for each weed were made used for comparison. Three counts for each weed were determine the level of infestation in each surveyed field. The percent yield reduction was then multiplied by the percent yield reduction was then multiplied by the from individual weed species. Several fields were checked in each county and data was averaged for weed species. Palmer pigweed, common cocklebur, and sicklepod caused the greatest yield loss (75%) in Lee County; while, common cocklebur reduced yields the most in Marlboro County. Corresponding estimates for yield loss are made in Table 1 for the entire state in the weed loss survey.