SummaryA comprehensive survey allowed to describe the different trends in the treatment modalities of hyperthyroidism with radioiodine applied in Belgium in 1985. Ii whs found that the mean dose admiuistred was moderate (whether a standard dose or a ealeulaled one was used) and that the aim was to avoid the advent of late hypothyroidism. Not one eenter had chosen to use ablative doses. Antithyroid drugs were extensively used a adjunctive therapy. mainly altei radioiodine administration. An age limit was set at 40 years in 90 of the belgian centers. It is discussed that these modalities are mostly based on theoretical considerations and that the modalities of the treatment of hyperthyroidism with radioiodine should perhaps be reassessed.