The records of 1,508 patients referred to the Nuclear Medicine laboratory of the University of Florida College of Medicine from 1958-1967 were examined for [See Tables in the PDF Files] determination of range of values of the PBI, T3, and 6 and 24 hour I131 uptake values in hypothyroidism, euthyroidism and hyperthyroidism. Mathematical formulae for ranges giving the least errors in classification are given. We have indicated that no single test by any formula can exactly predict the thyrometabolic status.