For the first time the results of GC-MS analysis of special simple of the Mentha piperita L. oil from Vietnam origin product from year 1975 are reported. The analysis was carried out on an Agilent Technologies 7890A system with 5975C MSD equipped with split-splitless injector (split, 250°C, split ratio 1:50, 0.1 L) and HP-5 ms capillary calibrated column (30 m x 0.25 mm x 0.25 m); The carrier gas: helium 1.1 mL/min; oven: 70°C - 2 min, 5°C/min - 200°C - 20 min - 300°C - 5 min; MSD in scan 30 - 300 amu, 15 min, 30 - 450 amu. The obtained chromatogram was compared to the results from the literature [1,2], and it differs by composition (mass spectra) and the ratio (A%) of the identified compounds. The major compounds detected by mass-spectometry are: (-)-Menthone (5.47%); Neoisomenthol (7.69); (-)-Menthol (52.25%); (+)-iso-Menthol (0.94%); iso-Menthol acetate (2.11%); Myristic acid (1.05%); Isopropyl myristate (9.97%) and new discover compounds: Ciclohexanol, 5-methyl-2-(1-methylethyl)-sulphite (2:1) (0.53%); Acetylene dicarboxilic acid, di-(-)-menthyl- (0.53%); p- Menthone; 3-allylperoxy (6.79%); Diazoacetic acid, 2-isopropyl-5-methylciclohexyl ester (0.44%). The obtained results show that during long storage (about 45 years) under normal conditions sealed at room temperature, the oil will be altered due to catalytic and oxidative processes (photocatalysis, peroxidase and others).