A naturally occurring monoterpene related to limonene with antineoplastic activity. Perillyl alcohol inhibits farnesyl transferase and geranylgeranyl transferase, thereby preventing post-translational protein farnesylation and isoprenylation and activation of oncoproteins such as p21-ras, and arresting tumor cells in the G1 phase of the cell cycle. or A substance that is being studied in the prevention of cancer. It belongs to the family of plant drugs called monoterpenes.