Possibility of producing (14C)-macrocyclic trichothecenes (MCTC) with high specific activity was studied. (1-14C)-glucose, (2-14C)-acetate and (2-14C)-mevalonate were used as precursors. The best results were obtained when labeled acetate was introduced into the medium at the end of the logarithmic growth stage of Dendrodochium toxicum 5800, a fungus-producer. Individual (14C)-MCTC with high specific activity are obtained: verrucarine A-158.1 microC/mM, rhoridine A-167.4 microC/mM; rhoridine H-161.9 microC/mM.