Present report deals with the essential oil components from Mentha japonica and a small mint of M. arvensis type grown wild in Hirennuma and Bansei-oikamanainuma, Hokkaido. The plant form of each the mint of M. arvensis type was similar to that of Mentha arvensis, though these could not run to seed both of them. The essential oils of M. japonica in above two area consisted mainly of limonene (0.3～2.4%), menthone (12.2～13.5%), isomenthone (0.3～0.5%), β-caryophyllene (4.1～7.6%), pulegone (64.3～68.0%),α-humulene (1.2～1.9%), germacrene D (2.5～2.9%) and germacrene D-4-ol (1.2～1.6%) from each plant harvested at flowering time. While the oils of M. arvensis type mint in above two area were composed of β - myrcene (0.1～1.2%), limonene (1.0～27.3%), (Z)-β-ocimene (0.1～1.7%), (E)-β-ocimene (t～2.1%), menthone (4.1～18.9%), isomenthone (0.2～0.7%), linalool (22.2～23.5%), β - caryophyllene (4.0～8.7%), pulegone (7.7～38.7%), α -humulene (0.8～1.3%), germacrene D (1.7～6.6%) and bicyclogermacrene (0.4～3.6%) and germacrene D-4-ol (0.8～2.9%) from each plant harvested at blooming time. It seems that two mints of M. arvensis type were F1 hybrids between M. japonica containing mainly of menthone and pulegone and M. arvensis containing mainly of linalool
