Boron (B) has great importance in the fertilizer recommendation programs of olive, since B deficiency is a frequent nutritional disorder. This paper reports results of the olive response to applied B from two 3-year field trials (ExpF1, ExpF2) and two pot experiments (ExpP1, ExpP2). The ExpF1 was installed in a 3-year-old orchard and the ExpF2 consisted of planting young trees with the aboveground biomass yield being recorded. In ExpP1, B was applied to the soil or as a foliar spray to the whole of the canopy. The ExpP2 consisted of the application of B to selected parts of the canopy. The concentration of B in the existing tissues receiving the spray directly and in the new shoots developing after the B application was determined. The performance of the crop, including olive yield, did not increase in ExpF1 with soil-applied B. However, dry matter yield of young plants in ExpF2 significantly increased with B application. The application of B, both as a soil fertilizer and as a foliar spray, significantly increased the B concentration in all tissues and in all experiments. From ExpP1, soil applied B proved to be a more powerful tool of delivering high amounts of B to the plant than foliar spray. From ExpP2, B was shown to be mobile in the tree to some extent, although the mobility appears to be cultivar-dependent. In 'Arbequina' the older leaves that received the foliar spray showed higher B levels than the young leaves that developed thereafter, whereas in 'Cobrançosa' this difference was not observed.