Achieving local control in patients with advanced adenoid cystic carcinoma continues to be a therapeutic challenge. From 1984 to 1990, we treated 34 patients with advanced adenoid cystic carcinoma of the head and neck with fast neutron radiation. Patients treated for minimal microscopic disease following surgery were not included in this study. Neutron radiotherapy achieved 5-year actuarial local control and locoregional control rates of 76% and 63%, respectively. Five-year actuarial overall survival and disease-specific survival rates were 65% and 93%, respectively. Eighty-one percent (17/21) of patients treated with neutron therapy alone and 100% (13/13) of the patients treated with neutron therapy and surgery achieved local control. All seven patients with paranasal sinus malignant neoplasms achieved local control. The success achieved in this prognostically unfavorable population affirms the important role of neutron radiotherapy in the treatment of adenoid cystic carcinoma.