Although the case for thyroid surgery is based on morphologic and physiologic criteria, it is mainly based on individual therapeutic goals. The goals are influenced by various biographic, medical and personal facts and by many environmental conditions. Thus, there is no rationale for cataloguing indications. With the euthyroid goitre the indication for surgery is usually given by the size of the thyroid gland, especially since it has become clear in various studies that with drug therapy the achievable size reduction is rather small. With Graves' disease the pros and cons of the three main methods, surgery, medical treatment or radioiodine, have to be considered in each case. Surgery is mainly indicated when the goal is a rapid and reliable normalization of the hormonal status. Thyroid autonomy is a clear-cut case for radioiodine. Only isolated autonomous nodules can equally well be treated by surgery. In addition, a case for surgery is given when besides the autonomy a large goitre is present. A special indication is iodine-induced thyrotoxicosis that cannot be normalized by medical treatment. All kinds of thyroid carcinoma, with very few exceptions, usually have to be operated on as the first choice.