PREP(TM) ethephon plant regulator applied at the proper rate to cotton that has a sufficient load of mature, unopened bolls will accelerate boll opening and enhance defoliation, while also removing immature fruit structures. An application of PREP(TM) will advance cotton harvest (seven to 10 days) and allow for a once-over harvest with spindle pickers. The effect of PREP(TM) on cotton classification has been extensively tested throughout the cotton belt since 1978 and this data will be presented. Results from tests in 1985 on the effects of PREP(TN) on cotton seed quality and fiber quality for spinning utilization by the mills will be discussed.