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When [4–¹⁴C]pregnenolone was aerobically incubated in vitro in the presence of NAD⁺ and NADPH with cell-free homogenates of testicular tissue of adult domestic goats (Capra hircus), progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, 17,20-dihydroxy-4-pregnen-3-one, dehydroepiandrosterone, androstenedione and testosterone were identified as its known metabolites. Time-course studies on this metabolism showed that the production of 17,20-dihydroxy-4-pregnen-3-one and testosterone constantly increased up to the end of incubation, suggesting that these are both end-products of pregnenolone metabolism in this system. The other metabolites behaved as intermediates and were ultimately converted, in part, to testosterone by the testicular homogenates, indicating that testosterone was synthesized through both 4-ene and 5-ene-pathways. Furthermore, besides these metabolites, 5-pregnene-3β,17,20-triol was also identified as an intermediary metabolite, formed from pregnenolone through 17-hydroxypregnenolone in the presence of NADPH, and further convertible into 17,20-dihydroxy-4-pregnen-3-one by the microsomal fraction and into 17-hydroxypregnenolone by the cytosol fraction in the presence of NAD⁺ and NADP It was not, however, significantly transformed into C₁₉-steroids. Furthermore, 17,20-dihydroxy-4-pregnen-3-one, which was formed either from 5-pregnene-3β,17,20-triol or from 17-hydroxyprogesterone, remained almost unchanged without conversion to C₁₉-steroids when incubated with the caprine testicular homogenates.