Large doses of radioiodine were administered since 1969 to 15 euthyroid patients with compressive voluminous goitres. A decrease in goitre size was observed in all patients (between 15 and 63%, average 39%). Maximal effect on goitre size was attained rapidly, partially already after less than one year and was almost maximal after 24 to 30 months. No significant local adverse reactions were observed; no patient required steroid administration. Hypothyroidism followed radioiodine administration in 30% of the patients after 2 years; after 8 years, all those who had survived were hypothyroid, requiring substitution therapy. In all patients there was a marked improvement in compression symptoms. The use of radioactive iodine therapy constitutes an alternative to surgery in selected patients with large compressive goitres in whom surgery is contraindicated because of age or other medical conditions.