In this study, pumpkin seeds, called as "Urgup Sivrisi" and grown in Cappadocia region, were used as plant materials because of high aroma contents. In the supercritical fluid extraction of pumpkin seed oil, the effect of main process parameters as the particle size (250-2360 mu m), the volumetric flow rate of supercritical solvent (0.06-0.30 L/h), the operating pressure (20-50 MPa), the operating temperature (40-70 degrees C), the type of entrainer (ethanol and n-hexane) and those concentrations (0-10 vol.%) on the extraction yield, the oil solubility and the initial extraction rate were investigated. A cross-over effect for the extraction of pumpkin seed oil using supercritical CO(2) was determined at the operating pressure of 20-30 MPa. The maximum extraction yield obtained with entrainer free was reached 0.50 g oil/g dry seed at 600-1180 mu m. 0.12 L/h, 50 MPa and 70 degrees C for the operation time of 5 h. The maximum extraction yield obtained with ethanol as an entrainer in the experiments was reached 0.54 g oil/g dry seed at the conditions of 600-1180 mu m. 0.12 L/h, 30 MPa, 40 degrees C and 8 vol.% for the operating time of 2 h. The oil compositions were determined by gas chromatography analysis and the results showed that the compositions of pumpkin seed oil which were obtained by means of organic solvent extraction and supercritical fluid extraction were similar. The average oil compositions determined as 9.3 (+/- 0.43)% palmitic acid, 7.5 (+/- 0.6)% stearic acid, 32.3 (+/- 0.6)% oleic acid, 48.1 (+/- 0.6)% linoleic acid and 0.7 (+/- 0.3)% linolenic acid. The morphological changes in the seeds were determined by the scanning electron microscopy analysis. (C) 2011 Elsevier B.V. All rights reserved.