To study the formation of 16-unsaturated C_<19> steroids from pregnenolone by human adrenal in　vitro, normal and abnormal adrenal tissues were incubated with ^3H- or ^<14>C- labelled pregnenolone and the metabolites were analyzed.
1) Normal tissue was obtained from a 51 year-old woman with pyonephrosis, and the tissue was found to have produced androst-16-en-3β-ol, in addition to cortisol and many other steroids which are well known to be biosynthesized. 2) The tissue obtained from a 19 year-old woman with Cushing's syndrome metabolized pregnenolone mainly to 11-hydroxysteroids, and to several other compounds in small quantities. Dehydroepiandrosterone and androst-16-ene derivatives were not produced in detectable quantities. 3) Adenoma tissues were obtained from a 5 year-old boy with Child-Hercules and a 44 year-old woman with virilism. The former's tissue produced androst-16-en-3β-ol while the latter's andosta-5,16-dien-3β-ol. Neither 11-hydroxysteroids nor dehydroepiandrosterone was formed by the latter tissue in detectable quantities.