Among 31 patients with de Quervain's thyroiditis (confirmed by biopsy in 15) there were seven who had an acute course. It is, therefore, suggested that the misleading term "subacute" thyroiditis for this form of inflammatory thyroid disease be avoided. It is nowadays the most frequent form of painful thyroiditis seen in clinical practice. Extremely rapid ESR with normal peripheral leucocyte count is a typical finding. Generally the disease is completely cured within a few weeks to months, transition to an immunothyroiditis or hypothyroidism being rare. Conventional antiinflammatory drugs, combined with thyroid hormone, give a good therapeutic response. Corticoids should be used only in exceptional instances.