A two-liquid-phase bioreactor was designed to extract indole alkaloids from Catharanthus roseus hairy roots with silicon oil. Partition studies between silicon oil and culture medium showed that the silicon oil did not alter the availability of nutrients. The affinity of tabersonine and lochnericine for silicon oil is nine times higher than for the aqueous phase. Cultures were elicited with 25 mg/L of jasmonic acid. The growth of the hairy roots was not significantly modified by the presence of silicon oil. The overall specific yields of tabersonine and lochnericine were increased by 100-400% and 14-200%, respectively, with the use of silicon oil in nonelicited control cultures. In elicited cultures, these values were 10-55% for tabersonine and 20-65% for lochnericine. Serpentine was never found in the silicon oil. All measured alkaloids' specific yields were higher using silicon oil and elicitation, suggesting that the silicon oil, while acting as a metabolic sink for tabersonine and lochnericine, was efficient in increasing metabolic fluxes of the secondary metabolism pathways.