The composition profile of horsetail (Equisetum giganteum L.) oleoresin obtained by supercritical fluid extraction (SFE) and organic solvents such as hexane and dichloromethane (DCM) was investigated and the results were compared to evaluate the processes efficiency. To observe the selectivity characteristic of the supercritical fluid process, carbon dioxide was used as solvent with density varying from 719.1 to 923.0 kg/m(3). The operating conditions were 303 and 313 K and 12, 15, 17, 20, 25 and 30 MPa and the SFE yield was up to 1.44% (w/w). In order to investigate the extraction process of the horsetail oleoresin, the main subject of this work was the qualitative evaluation of the extracts by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis, due to the non-polar characteristic conferred by the supercritical solvent. The compounds identification of the horsetail extracts was based on a database for natural products. The influence of the solvent density and the extraction time in the oleoresin composition was also investigated. The evaluation of the composition profile indicates that the supercritical CO2 extracts are remarkably different than the organic solvent extracts. (C) 2004 Elsevier B.V. All rights reserved.