Different oil-samples of Melissa officinalis L. were analysed by capillary GC/MS, using fused silica columns and E.I.-Mass-spectrometry. Comparing the observed mass-spectra with those of a spectral collection, 70 compounds of the oil were identified. Geranial, neral, 6-methyl-5-hepten-2-one, citronellal, geranyl-acetate, beta-caryophyllene, and beta-caryophyllene-oxide comprise about 96%. The fingerprint of the capillary gas-chromatogramm permitted differentiation of the essential oil of Melissa officinalis, Cymbopogon winterianus and Nepeta cataria var. citriodora., as well as a standardisation of pharmaceutical preparations containing Melissa oil.