Hiprose seed oil has been extracted by supercritical CO2 operating at pressures of 1500, 3000, 6000 and 10 000 psi, temperatures of 40, 50 and 70 degrees C, CO2 flow rates of 1, 2, 4 and 6 g/min using mean particle sizes of 0.42, 0.79 and 1.03 mm. The obtained oil! yield data has been used to validate a mathematical model of the extraction process, based in part on the information obtained from the microscopic structure of the hiprose seed particles. The differential mass balances forming the model have been numerically integrated. The best fit between model curves and data has been obtained when a linearly variable internal mass transfer coefficient was adopted: with an initial value of 1.9 x 10(-5) m/s.