[en] The method of direct saturation analysis using a Trilute kit was evaluated. The net retention did not change with different eluting speeds but it increased at higher temperatures. The coefficient of variation (C.V.) within the assay was 2.5%. The percent retention, which was calibrated for values at 25⁰C, was 48+-7.1% (mean +- standard deviation) in euthyroid subjects, 73+-9.8% in hyperthyroidism, and 28+-3.6% in hypothyroidism. Coefficient of correlation between Trilute and Triosorb values was 0.88. In vitro addition of a larger amount of diphenylhydantoin (500 μg/ml), and salicylate (4 mg/ml) to the serum induced higher values with Trilute and Triosorb. (auth.)