BACKGROUND: It has been recommended that cobalt-60 or 4-MV photons be used when treating glottic cancer with radiation therapy. Underdosing may occur when using higher energy photons, particularly when the anterior commissure is involved. The authors report their experience using higher energy photons (6 MV) for the treatment of glottic cancer. METHODS: Between January 1975 and July 1991, 73 patients with Tis, T1, T2, or T3 glottic tumors underwent radiation therapy with curative intent. Cobalt-60 or 4-MV photons were used to treat the cancers of 30 patients, and 6-MV photons were used to treat 43 patients. Clinical records were reviewed retrospectively to determine patterns of treatment failure, cancer deaths, and local tumor control in the 43 patients receiving treatment with 6-MV photons. Patients were followed until death or for a minimum of two years. RESULTS: Treatment failures were: local recurrence, one patient; local recurrence and distant metastasis, one patient; delayed neck metastasis, two patients; and delayed neck metastasis with distant metastasis, one patient. Three patients who had treatment failure are alive and free of cancer after salvage treatment. Two patients died of neck and distant metastases. The 2-year initial local tumor control rate was 94.8%. CONCLUSIONS: Glottic cancer can be treated successfully with 6-MV photons. Local tumor control is similar to that reported using cobalt-60 or 4-MV photons.