The impact of leaf and fruit damage on cotton's growth, development, maturation, and yield differs and is dependent upon the stage of crop growth during which it occurs. Damage to terminal apical meristem tissues, as would be caused by early season thrips or worm pests, although not affecting yield, can result in a delay in crop maturity of up to ca. 2 weeks; earlier the damage, greater the delay. Damage by sucking arthropod pests, such as mites or thrips, has the greatest impact on yield earlier the damage. Cotton, however, can tolerate fairly high levels of surface feeding damage. In the case of mites, yield loss will not result even when 80% of sampled leaves are infested. Defoliation damage as would be caused by beet armyworm, cabbage looper, or saltmarsh caterpillar has the greatest impact upon yield when occurring during the period of square production and rapid boll set. Defoliation damage occurring prior to the initiation of squaring appears to stimulate the plants to produce yields greater than what would be achieved in the absence of damage. Defoliation damage occurring after most of the bolls have matured has no effect on crop yield. Damage to fruiting structures reduces yield the most when occurring during the period of rapid boll maturation. Fruit damage occurring prior to flowering will conversely often result in the crop overcompensating and result in a yield increase. Fruit damage during the peak squaring early boll period normally has no effect on either yield or crop maturity. As the margin between costs and profits continues to decrease, and as insecticide and environmental-related problems increase, cotton managers must, through necessity, incorporate into their pest management philosophy the concept that some damage can be sustained without reducing crop profitability.