This research was carried out to determine the effect of boron fertilization on the hollow stem development in broccoli under field conditions, in 2016-2017. In the study, three broccoli cultivars (Brassica oleracea var. italica, Plenk cvs. 'Batavia F1', 'Burney F1' and 'Lucky F1') were used as plant material. In addition, boron was applied at 0, 1, 2, 3 kg B ha -1 . It was determined that the effect of boron applications on the hollow stem development in broccoli varied according to the cultivars and boron doses. It was clearly said that the most sensitive cultivar to the development of the hollow stem is Burney F1 (35%) and the most resistant cultivar is Lucky F1 (15%). The percentage of the hollow stem was the highest in control in all cultivars used in this study. It has been determined that the effect of boron applications reduces the percentage of hollow stem formation at different rates, although it varies according to the cultivars. According to the results of the research, Lucky F1 and 3 kg B ha -1 boron application can be recommended for broccoli growers to overcome the formation of the hollow stem that is an important physiological disorder in broccoli, especially in similar ecologic conditions.