Alpha-bisabolol is a compound present in some essential oils, widely distributed in several plants, including camomile. Two different methods for analysing an essential oil, such as alpha-bisabolol in human blood are reported: the first uses micro-liquid chromatography-electrospray ionisation-mass spectrometry (muHPLC-ESI-MS), whereas the second is based on "head space" injection coupled to gas chromatography-mass spectrometry (HS-GC-MS). For LC-ESI-MS, human blood samples, spiked with alpha-bisabolol, were extracted with hexane and evaporated to dryness under air stream. The residue was then reconstituted with methanol and injected into a C18 column, connected to an ion trap mass spectrometer equipped with an ESI source. Spectra were recorded in the positive ion, selected ion monitoring mode. The detection limit of alpha-bisabolol in blood was 0.125 micromol/l. The preparation of samples for the analysis in HS-GC-MS was limited to blood dilution with water (0.5 ml blood + 1 ml water). Head space vials were heated at 125 degrees C for 1 h before automatic injection. The HS-GC-MS detection limit (0.13 micromol/l) was similar to that achieved with the muHPLC-ESI-MS method. Successful tests were performed to verify if alpha-bisabolol could be directly measured by the HS-GC-MS method in different biological samples (blood, urine, faeces, homogenate tissues) from rats treated with the camomile essential oil.