Response of flowering and fruiting of Picual olive trees to paclobutrazol (PP333), uniconazole (UC), sitofex (CPPU) and boric acid (H₃BO₃ ) were tested during 1996/97 and 1997/98 seasons. PP333 and UC (250, 500 ppm) sprayed at pre bloom; CPPU (20 ppm) or H₃BO₃ (250, 500 ppm) at pre bloom or post bloom. PP333, UC and H₃BO₃ were effective to induce earlier emergence of inflorescences, increase the number of inflorescences and showed influence on sex expression percentages. H₃BO₃ was the most effective treatment to increase pollen germination and fruit set percentage. On the other hand, CPPU sprayed two weeks after full bloom yielded the largest and heaviest fruits and the highest flesh/fruit percentage. However, H₃BO₃ and CPPU treatments after FB resulted in higher fruit oil content.