Cost accounting has shown that the volume of tissue to be treated is the decisive factor in determining the cost of radioiodine therapy (RAITh). In the case of large goitres, the costs of excision (5.185 DM) and radioiodine therapy (5.562 DM) are, to a large extent, equivalent. Under the 1993 regulations for radiation protection, RAITh was cost-effective for treatment of toxic multinodular goitres up to volumes of 57 ml. However, new maximum permissible levels of radioactivity on discharge from hospital (250 MBq iodine-131 residual activity) have raised this threshold volume to 90 ml. In Germany, remuneration for a goitre resection is calculated from standard charges for total treatment without any consideration of the size and spectrum of medical services offered by different clinics, while remuneration for RAITh comes from payments for basic and specific, departmental medical services. University clinics with departments of nuclear medicine have relatively high basic costs. In the first quarter of 1998, the length of hospitalisation after RAITh (for all indications combined) was 4.6 days in university hospitals in Germany. Owing to this shorter length of hospitalisation, the payments received in some clinics fell far short of the total costs of this treatment calculated by cost accounting.