The indications for using sonography in the investigation of the thyroid gland are discussed. Correlation of echo patterns and thyroid disease has shown that sonography deserves a place in the diagnosis of thyroid disease in the same way as the classical methods, such as clinical examination, scintigraphy, laboratory investigations and aspiration biopsy. The indications for sonography, which are illustrated by a number of examples, include: 1) when scintigraphy cannot be used, 2) pre-operative demonstration, 3) disagreement between clinical findings and the scintigram, 4) diagnosis of cysts, 5)suspicion of thyroiditis.