The unstimulated and stimulated thyrocyte is able to produce more different cytokines in vitro than any other endocrine cell. Cytokines produced by thyrocytes may play a role in the local stimulation and maintenance of immune responses against autoantigens in the thyroid, in the modulation of goiter size in response to TSH, and in the clinical course of patients with thyroid tumors. This paper tries to summarize the results of relevant studies investigating cytokine production by thyrocytes. Although there is an agreement in published work that thyrocytes secrete a number of cytokines such as II-1, II-6, II-8 and TGF-beta in vitro it is unclear whether these factors are produced also by thyrocytes in vivo. By the example of GM-CSF in vitro secretion by stimulated anaplastic thyroid carcinoma cell lines and stimulated thyrocytes, the relevance of these findings during the clinical course of patients with anaplastic thyroid tumours is discussed.