The paper deseribes the determination of indium in metallic tin and cadmium metals by the direct method, which is a variant of substoichiometric radioactivation analysis. It is based on substoichiometric extraction of indium diethyldithiocarbamate into carbon tetrachloride. Indium in tin metal was determined by116mIn (T=54 min), while115mIn (T=4.5 h), formed by the reaction114Cd(n, γ)115Cd was used for cadmium samples. The irradiated sample was dissolved and the radioactivity of116mIn or115mIn, A, was measured. After the separation of indium from the matrix, a known amount of indium, m, was separated substoichiometrically and the radioactivity, a, was measured. Indium was calculated as Mx=m A/a. If a known amount of the element, M, is added to the irradiated sample in advance, the equation for calculation is given as Mx-m A/a−M. By this method, indium can be determined without any consideration of self-shielding and secondary nuclear reaction of the matrix.