Compounds possessing the skeleton of cyclopenta[a]phenanthrene or a skeleton derived therefrom by one or more bond scissions or ring expansions or contractions. Methyl groups are normally present at C-10 and C-13. An alkyl side chain may also be present at C-17. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. [ ]