An experiment was conducted to determine the effects of gibberellic acid (GA3) and the biostimulant folcisteine on growth and yield of yellow onion (Allium cepa L.) "Ben Shemen" under the conditions of Santo Domingo, Dominican Republic. Application of 10 ppm GA3 plus 10 ppm folcisteine gave the best results for bulb fresh weight, dry weight and diameter, which were significantly increased over those of control plants and the other combinations of the regulators tested.