PURPOSE: Study of thyroid function in Hodgkin's disease patients in complete remission. PATIENTS AND METHODS: We examined the thyroid function of 160 Hodgkin's disease patients in complete remission for at least one year, and determined the values of supersensitive thyroid stimulating hormone (sTSH), free T4 (fT4), free T3 (fT3) hormones. RESULTS: Normal values were observed in 117 patients, subclinical change (only elevated sTSH) in 28 patients, clinical hypothyroidism in 14 patients (also low fT4 and/or fT3), hyperthyroidism (Basedow's disease) in one patient. Hypothyroidism was one and a half times more frequent in females than in males. The normal and low thyroid function group did not differ from each other in mean age, histological subtypes, disease stage, general symptoms, and whether lymphangiography was performed. Hypothyroidism was more frequent in patients who had undergone mantle or neck radiotherapy. The onset of thyroid gland underfunction was more pronounced from six years after neck radiotherapy. The thyroid disease could be controlled using a daily dose of 25-225 mg levothyroxin. CONCLUSIONS: During the care of Hodgkin's disease patients routine examination of the thyroid function is important for the early recognition and prevention of treatment related late complications. On the other hand in treatment planning phase more attention should be paid to thyroid gland protection when neck radiotherapy is used.