Laryngeal necrosis is a serious complication that usually occurs within the first year following completion of radiotherapy, although it is reported that cases can develop after a long period of latency. Factors such as dosage and irradiation technique employed, tumour invasion into the laryngeal cartilage, infection, continued smoking, trauma and general vascular condition of the patient have been considered to increase the rate and degree of development of radionecrosis. We report an unusual case of laryngeal radionecrosis in a patient with hypertension, hyperlipidaemia, diabetes and a history of cigarette smoking, which developed 25 years after radiotherapy for laryngeal carcinoma. His systemic illnesses and continued smoking were speculated to have contributed to the progress of the radionecrosis, suggesting that cessation of smoking and control of arteriosclerotic diseases should be considered to decrease its incidence.