Labeled sodium acetate [carbonyl-14C] was given to Mentha arvensis L. var. piperascens HOLMES, and its utilization rate and distribution in the plant were examined. Menthol was isolated from the radioactive mentha oil obtained therefrom and it was found that the carbon atoms in 3-, 1-, and/or 8- positions of menthol originated from the carbonyl-carbon in the acetic acid while those at 7-, 9-, and 10-positions had no radioactivity.