⊿(4)-Cholestenone-4-C(14) metabolisms were studied with the nuclear, mitochondrial, microsomal and supernatant fraction. Enzymic activity of cholestenone to cholestanone was higher in nuclear and mitochondrial fraction, and the activity was higher about 2-4 times in tumor-bearing rat. This suggests the enzyme block from cholestenone to cholestanone. Inaceton powder, these enzymes were inactivated, and the enzymes were easisted in the fraction precipitated with the concentration of (NH(4))(2)SO(4) at 30g/dl.