Boll openers are often used when terminating a crop in order to open immature bolls and increase yields. A study was initiated in 1996 to test the effectiveness of four boll opening products for their capacity to open immature bolls. Two locations, Rocky Mount and Lewiston were used. Treatments were applied at Rocky Mount on Sept. 18 and at Lewiston on September 27. The treatments were Prep at 1.33 and 1.67 pints per acre, Starfire at 6, 11, 16, and 24 ounces per acre, CottonQuik at 2 and 3 quarts per acre, Finish at 1 and 1.5 quarts per acre, Def/Folex at 1.5 pints per acre, and an untreated control. At Rocky Mount, the four boll openers were tankmixed with 1.5 pints per acre of Def/Folex, and at Lewiston, they were tankmixed with 0.5 pints per acre of Def/Folex. Plots were four rows wide and 50 feet long. Hand harvests were taken every 3-4 days from 3 meters of one inside row of each plot. Data were analyzed as percent of total harvestable yield on each harvest date.