During the period from October 1964 to September 1975, 32 patients were treated at the University of Florida for a variety of malignant tumors of the nasal cavity and ethmoid/sphenoid sinuses. All were treated with radical irradiation, 6091 to 7972 rad, in 6 to 9 weeks, cobalt-60. Pretreatment work-up revealed evidence of orbital invasion in 7 patients and involvement of the cranial contents, base of skull, or nasopharynx in an additional 15 patients. Local control was achieved in 95% of nasal cavity cases and 71% of ethmoid/sphenoid sinus cases at 2 years or more. The 5-year actuarial survival rate was 59%, and 5-year survival without evidence of disease was 50% (13/26). Patterns of extension in advanced lesions are clues to potential undetected extension in early cases which must be included in the treatment volume. Eye complications were minimal when it was possible to avoid treatment of the entire eye, but developed in all cases requiring treatment of the entire orbit. Acute and chronic complications involving the eye, ear, central nervous system, sinuses, and nose were reviewed and correlated with initial tumor extent, dose, and radiation treatment technique.