Six neoplastically-derived cell lines and three cell lines derived from normal tissues were compared for their sensitivity to isoprenoid irons-trans farnesol. Assays of cell numbers and of protein concentrations per culture revealed greater sensitivity of neoplastic cells than of the normal cells. Similar differences were obtained from the comparison of incorporation of [methyl-H-3]choline into cellular lipids, with neoplastic cells showing greater inhibition than normal cells.