Homogenates of cerebral metastatic chorionepithelioma tissue were incubated with labelled dehydroepiandrosterone, pregnenolone or 20alpha-hydroxypregn-4-en-3-one. The metabolites of dehydroepiandrosterone which were isolated and identified were androstenedione, testosterone, oestrone, and oestradiol; no oestriol was detected. The only metabolite of pregnenolone and 20alpha-hydroxypregn-4-en-3-one isolated and identified was progesterone. No conversion of C-21 to C-19 steroids occurred in the metastatic chorionepithelioma tissue.