The constituents of monoterpene in Paeoniae Radix were analyzed by means of high performance liquid chromatography (HPLC) using hitherto elucidated eight monoterpene glycosides, paeoniflorin 1, oxypaeoniflorin 2, benzoylpaeoniflorin 3, benzoyloxypaeoniflorin 4, galloylpaeniflorin 5, galloyloxypaeoniflorin 6, albiflorin 7 and lactiflorin 8 and a monoterpene paeoniflorigenone 9. In sixty seven kinds of Paeoniae Radix collected in Japan, China, and South and North Korea those monoterpene constituents 1-9 were found to exist in the amounts of ranging 0.12-9.61% 1, 0.06-10.8% 2, 0.02-0.79% 3, 0.24-0.47% 4, 0.25-2.53% 5, 0.05-2.86% 6, 0.09-2.76% 7, 0.35-0.64% 8 and 0.01-0.49% 9 respectively. In addition, these results obtained by the quantitative analysis were discussed from the viewpoint of the external figures and processing methods.