Eleven olfactory neuroblastomas treated at Helsinki University Central Hospital between 1970 and 1991 were reviewed retrospectively. The distribution of the patients was according to Morita's staging (modified Kadish's classification) as follows: one stage A, one stage B and nine stage C. Tumor resections were performed in all cases, and five were considered radical. All patients received radiotherapy: total doses ranged from 42 to 70 Gy. At least a short treatment response was achievable in all cases. Chemotherapy was given to two patients: one remission was obtained by methotrexate with leucovorin rescue and doxorubicin for residual disease after radiotherapy. Distant metastases were observed in three cases, two in the lungs and one intraperitoneally. After a median follow-up of 63 (range, 6-140) months, five patients are alive and well, two patients have died with no evidence of disease; two patients who received only 42 and 50 Gy in 5 and 6 weeks have died of local recurrences and two of distant metastases. None of the patients with advanced (stage B or C) disease who received radical radiotherapy ( > or = 60 Gy given in 6 to 9 weeks) developed local recurrence. The increasing incidence of distant metastasis justifies an intensification of initial treatment, especially in state C disease.