Echography of the thyroid gland is a non-invasive and simple method without contraindications. The method is reliable, inexpensive and of high diagnostic efficiency. The structural information provided by the ultrasound technique complements the results of laboratory tests and other in-vivo techniques. Normal echogenicity can be observed in health persons as well as in diffuse goiters. An echofree area with enhanced echogenicity is a typical sonogram of a cystic structure. Circumscript enhanced echogenicity is usually due to a benign lesion. Areas of diminished echogenicity may be benign or malignant. In patients with Graves' disease or patients suffering from lymphocytic thyroiditis, diffuse diminished echogenicity is found in a high percentage. CT of thyroid masses allows an exact measurement of the volume of the organ to be made together with its retrosternal parts. CT examinations can locate the spread into the frontal and posterior mediastinum, thus providing optimal operative access to retrosternal goiters. Remnants of thyroid malignancies, lymph-node metastasis, infiltration into the sternum and occlusions of larger vessels due to tumour growth are visible in the CT-Scan. It is not possible to differentiate between malignant tumours or benign masses, if there is no infiltration into the surrounding organs. Also hyperthyroidism and thyreoiditis cannot be differentiated. In our opinion ultrasound examinations should immediately follow the patient's history and physical examination. Additional in-vivo methods should be performed according to the specified problems.