A field experiment was carried out in 1978/79 in Piracicaba, Sao Paulo State, Brazil, to study mepiquat chloride (DPC). chlorocholine chloride (CCC) and ethephon (CEPA) effects as plant regulators on cotton. The treatments were DPC 84, 167 and 250 ppm, CCC 250, 380 and 450 ppm, and CEPA 1670, 3340 and 6880 ppm, applied 51, 65 and 143 days after germination, respectively. CCC and DPC caused reduction on plant growth and diminution on growth analysis parameters. The number of productive branches and balls number were not afected by CCC and DPC. Variations on productivity parameters were observed, but CCC, DPC and CEPA showed a tendency to increase the average weight of cotton in each plant. The growth substances used did not affect the agronomic and technological characters of cotton.