Abstract Cotton ( Gossypium hirsutum L.) plants that had approximately 65% open bolls were sprayed with DEF (S,S,S-tributyl phosphorotrithioate), ethephon [(2-chloroethyl)phosphonic acid], arsenic acid, and paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) to determine the effects of the chemicals on boll dehiscence, seedcotton yield, and quality of seed and fiber. All chemicals except DEF increased boll dehiscence rate and first harvest percentage. The greatest effect on these two parameters occurred in the ethephon-treated plots. Total seedcotton yield was not affected by either DEF or ethophon, but was reduced significantly by treatments with either arsenic acid or paraquat. In addition, the fiber micronaire readings of the lint gathered at first harvest was reduced by arsenic acid and paraquat treatments. All chemical treatments had an adverse effect on one or more of the components of bolls that were unopened at treatment time. Boll size and fiber micronaire were reduced by treatments with ethephon. DEF caused a reduction in boll size only, whereas arsenic acid and paraquat caused reduction in boll size, seed index, lint index, fiber micronaire, and seed germination. These results indicate that growth regulator chemicals can be used to accelerate boll dehiscence and increase firsth harvest percentage, though the quality of the harvested product may be lowered if treatments are made when many immature bolls are present.