The clinical reasons for requesting in-vitro thyroid-function tests were studied in 500 consecutive new patients with no known history of thyroid disease. 23 patients presented with five or more signs or symptoms of thyroid disease, and 18 of these required treatment for thyrometabolic dysfunction. Of 35 subjects with three or four thyroid-associated signs or symptoms, only 1 came to treatment. Of 442 subjects with one or two signs or symptoms, 2 were subsequently treated. These results suggest that there is little value in the biochemical investigation of patients who present with minimal clinical evidence of thyrometabolic disease.