The authors present a radioimmunological method for determination of insulin (IRI) level in the human serum using magnesium silicate (talc) as adsorbent. The method is based on the phenomenon of selective adsorption of the free radioactive hormone. The optimal parameters for the method were determined. The serum level of IRI in clinically healthy subjects after oral glucose loading was established. The obtained results were compared with the results obtained by the radioimmunological method of double antibodies in stochastically grouped samples.