Complications of antiresorptive therapy that occur in patients with cancer and systemic osteoporosis are of great interest to practicing physicians. The insufficient level of knowledge among dentists about the pharmacodynamic effects of antiresorptive drugs leads to the development of a serious, difficult to treat complication — drug-associated osteonecrosis of the jaw bones. The article is a description of a clinical case of the development of osteonecrosis of the upper jaw in patient K. with a burdened history of cancer, who had previously received zoledronic acid and denosumab. Osteonecrosis developed after surgery to excise fibromatous epulis in the area of teeth 1.3 and 1.4. The article describes the possible causes of the disease in this patient and discusses possible treatment methods.