Most plant growth regulators have overlapping functions. Elevated ethylene levels have been implicated in the abscission of young cotton fruit and boll opening. Different plant cell types also differ in their sensitivity to growth regulators. The ethylene-generating compound, 2-chloroethyl phosphonic acid (CEPA), has been reported to cause excessive callus formation on cotton ovules cultured in vitro. In order to avoid this problem the culture period was reduced from two weeks to three days.Ovules were pretreated with gibberellic acid (GA(3)) for six hours and then placed in media containing no GA(3) GA(3), CEPA, or GA(3) + CEPA. Fiber elongation was inhibited by GA(3) (5.6µM) + CEPA (20µM); CEPA alone did not promote or inhibit fiber elongation. Cell suspension cultures (ovule-derived) were treated with GA(3) (5.6µM) or GA(3) + CEPA. In cells treated with GA(3) + CEPA (2µ) expansion was inhibited in the longitudinal direction and promoted in the lateral direction; at 1µM CEPA only lateral expansion was promoted. These findings demonstrate that cell suspension cultures and ovule cultures respond to GA(3) + CEPA in a similar manner. More dramatic changes in cell morphology were seen in suspension cultures.