The radiotherapy of advanced and low grade tumors of the internal nose and paranasal sinuses is still a problem. The results of neutron therapy of 20 patients with advanced and low grade tumors are presented. These patients were treated between July 1977 and October 1988. The mean age of patients is 53 years. Ten patients had adenoid cystic carcinomas, three patients squamous cell carcinomas, one patient a mucinous cell carcinoma, two patients a low grade adenocarcinoma and four patients low grade sarcomas. Mean follow-up is 16 months. Local control could be achieved in eleven cases. The results show that adenoid cystic carcinomas, low grade adenocarcinomas and sarcomas benefit from neutron therapy.