Effects of foliar spray of boron in fall on flower development and fruit set the following spring in `Satohnishiki' sweet cherry grown in warm areas were studied. All leaves of potted trees were sprayed with boric acid solution (B at 500 ppm) in early September. The boron treatment prolonged the ovule longevity and accelerated the elongation of pollen tubes in pistils the following spring. As a result, the fruit set rate of boron treated trees was higher than that of control trees. These results suggest the possibility of applying foliar spray of boron in fall to increase fruit set the following spring in sweet cherries grown in warm areas.