Technical Abstract: Organic production practices, urban encroachment and the presence of certain protected crops on adjacent fields presently restrict the use of defoliant chemicals in some cotton acreage. New legislation or stricter interpretation of existing environmental regulations may greatly increase the amount of cotton acreage where organophosphate defoliants are prohibited. The US cotton industry is preparing to meet this possible challenge by developing crop termination technology that uses heat instead of chemicals. An experimental thermal defoliator was operated in California, New Mexico and Texas in 2002. A larger prototype unit was used from 2003 to 2006 for extensive trials in a variety of field conditions and cultivars. This paper summarizes physiological studies showing the efficacy of thermal defoliation and its impact on yield and harvest timing, fiber quality studies indicating no damage to lint value and entomological studies demonstrating reduced late season pest populations.