After incubation of progesterone with the soluble and the gel filtrated fraction, Which were obtained from boar testicular homogenate, androst-16-ene compounds were identified by gas chromatogtaphy mass spectrometry. The soluble fraction produced androsta-4,16-dien-3-one and androsta-5,16-dien-3-ol while the gel filtrated fraction only androsta-4,16-dien-3-one. Neitber androst-16-en-3α-ol nor androst-16-en-3β-ol was formed by both fractions in detectable quantities.