A patient with suppurative thyroiditis due to infection with Escherichia coli is described. Serial studies of thyroid function were performed. Before the abscess was drained there was no uptake of radio-I by the thyroid and there was some spillage of iodinated compounds from the gland. Post-operatively circulating thyroid hormone concentrations declined but were restored at 4 wk. Thyroid uptake of radio-I was re-established 2 wk after operation but there was little secretion of thyroxine at this time. Four wk after operation, the uptake of radio-I was greater than normal and thyroxine was being secreted. These changes in thyroid function were not associated with any significant rise in the plasma thyrotropin concentration.