Cotton (Gossypium hirsutum L. ‘Stoneville 213’) was grown with densities of sicklepod (Cassia obtusifolia L.) or redroot pigweed (Amaranthus retroflexus L.) ranging from 0 to 32 weeds/15 m of row. Regression of seed cotton yields on weed density revealed a linear decrease in yield with increasing weed densities. In the 3 yr these studies were conducted, losses in hand harvested yields of seed cotton ranged from 34 to 43 kg/ha for each sickledpod plant/15 m of row and 21 to 38 kg/ha for each redroot pigweed plant per 15 m of row. Under comparable weed densities, yields of seed cotton differed only slightly when hand harvested or mechanically harvested. Mechanical harvesting efficiencies of cotton were reduced only at higher densities of weeds. The percentage of trash in cotton generally increased with increasing density of weeds. Neither sicklepod nor redroot pigweed affected cotton grade or micronaire.