Trace amounts of labelled pregnenolone were added to the slices of veriliscent tumor from human adrenal gland in order to study the stepwise conversion of the steroid into androstenedione, 11betaOH-androstenedione and their intermediats--17-alpha-OH pregnenolone, dehydroepiandrosterone, progesterone, and 17-alpha-OH-progesterone. The definite sequence was observed in the maximal incorporation of pregnenolone label into 17-alpha-OH-pregnenolone (2-5 min of incubation) leads to dehydroepiandrosterone (5-15 min) leads to androstenedione (10-20 min). Incorporation of the pregnenolone label into 17-alpha-OH-pregnenolone and dehydroepiandrosterone was distinctly higher than into progesterone and 17-alpha-OH-progesterone in all the experiments within all the studied periods of incubation. The data obtained suggest that in viriliscent tumors of adrenal gland conversion of pregnenolone into androgens proceeded as follows: pregnenolone leads to 17-alpha-OH-pregnenolone leads to dehydroepiandrosterone leads to androstenedione. When formation of androstenedione and 11beta-OH-androstenedione from pregnenolone and progesterone was analyzed during the experiment it was shown that 11-beta-OH-androstenedione was mainly formed via androstenedione and the hormone was the end product of the androgen synthesis.