Oil was extracted from the peach (Prunus persica) seeds by supercritical carbon dioxide. Principal phytosterols (stigmasterol, campesterol and beta-sitosterol) that have been known to have cholesterol lowering properties were investigated in the extracted oil. Based on gas chromatography-mass spectrometry (GC-MS) analysis, beta-sitosterol was identified in the peach seed oil. The effects of temperature, pressure, flow rate of supercritical CO2, mean particle size of the seeds and extraction time on the amounts of extracted oil and beta-sitosterol were investigated. Supercritical fluid extractions were performed in a range of 35-55 degrees C, 160-240 bar, 4-8 ml CO2/min, 0.3-1.7 mm and 1-4 h for mentioned parameters. The results indicated that the amounts of oil and beta-sitosterol extracted from the peach seeds were optimal with values of 35.3 g/100 g seed and 1220 mg/kg seed respectively at 40 degrees C, 200 bar, 7 ml/min, 0.3 mm and 3 h. (C) 2014 Elsevier B.V. All rights reserved.