Supercritical fluid extraction represents an efficient and environmentally friendly technique for isolation of phytosterols from different plant sources. Sea buckthorn (Hippophae rhamnoides L.) seeds were extracted with supercritical carbon dioxide at pressures ranging from 15-60 MPa and temperatures of 40-80 degrees C. Oil and beta-sitosterol yields were measured in the extraction course and compared with Soxhlet extraction with hexane. The average yield of beta-sitosterol was 0.31 mg/g of seeds. The maximum concentration of beta-sitosterol in the extract, 0.5% w/w, was achieved at 15 MPa, 40 degrees C, and a carbon dioxide consumption of 50 g/g of seeds. The extraction rate was maximal at 60 MPa and 40 degrees C. Both beta-sitosterol yield and its concentration in the extract obtained with hexane were lower than with carbon dioxide.