The essential oils of 10 authentic coriander samples of different origin were analyzed. Capillary gas chromatography, on-line coupled with isotope ratio mass spectrometry (cGC-IRMS) using Stabilwax as the stationary phase, was applied. Alternatively, heptaxis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin in PS 268 was used as the chiral stationary phase. The enantiomeric ratio and the delta(13)C(PDB) values of some characteristic-compounds were compared with those of commercially available spices and essential oils. The influence of isotopic effects on the delta values during the primary CO2 fixation was eliminated by definition of a suitable internal isotopic standard (i-IST). The isotopic effects among genuine monoterpenes are, therefore, exclusively determined by the influence of enzymatic reactions during secondary biogenetic pathways.