Container experiments were conducted in the Dominican Republic to determine the effect of gibberellic acid-3 (GA3), folcysteine and kinetine on the competitive ability of eggplant against the weed purple nutsedge. Eggplant transplants were treated with the growth regulators immediately before transplanting. The rates were 25 and 50 ppm for GA3 and kinetine, and 250 and 500 ppm for folcysteine. The competitive ability of eggplant against nutsedge was determined by relative crowding coefficients (RCC) in a replacement series with five eggplant to purple nutsedge proportions (4:0, 3:1, 2:2, 1:3 and 0:4). Kinetine and folcysteine were not effective in increasing the ability of eggplant to compete against purple nutsedge. When no plant growth regulators were used, eggplant was more competitive than nutsedge. As GA3 was applied at a rate of 25 ppm, eggplant competitiveness raised with respect to the control for the 3:1 (+73%), 2:2 (+107%) and 1:3 (+24%) ratios, whereas purple nutsedge RCC values decreased 33, 50 and 50% for 3:1, 2:2 and 1:3 proportions. When 50 ppm of G A3 were sprayed, eggplant aggressivity was enhanced even further with increases of 98, 104 and 55% at the 3:1, 2:2 and 1:3 proportions.