Hodgkin's disease appearing as, or associated with, fibrous thyroiditis has only been described rarely. We report the observation of a patient presenting with a goitre, fibrosis of the thyroid and adjacent structures, and hypothyroidism. The histological examination was compatible with fibrosclerotic thyroiditis. This diagnosis was reviewed 6 months later when the biopsy of a supraclavicular nodule that had subsequently appeared led to the diagnosis of a nodular-sclerosis type of Hodgkin's disease. The plasmatic levels of interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) were very high compared to the levels in healthy subjects (12 and 40 IU/l vs. 0.05 and 2.0 IU/l, respectively). These cytokine levels decreased when the initial illness was treated, and their normalization was associated with the disappearance of the cervical and thyroidal fibroses. A parallel in vitro study of these cytokines and of TNF-alpha receptors and IL-13 was performed. The results suggest a possible cause-and-effect relationship between IL-6 and IL-13 produced locally by the tumoral tissue and the development of cervical fibrosis.