This study examines pressurized hot water extraction of anthraquinones from dried roots of Morinda citrifolia (Noni). The effects of various operating conditions such as water temperature (110, 170, and 220 degrees C), and water flow rate (2, 4, and 6 mL min(-1)) on extraction yield and extraction rate were determined. At 220 degrees C, the extraction yield was the highest and was approximately 43.6 mg g(-1). Subcritical water extraction at 4 mL min(-1) or higher was found to be able to recover all the antraquinones present in the roots within 3 h of extraction, even at 170 degrees C. Pressure had no significant effect on the results for the range of temperatures studied. The flow rate of 6 mL min(-1) resulted in the highest extraction rate, but the extraction efficiency, as measured by the amount of anthraquinones extracted per unit volume of water was lower than that of 4 mL min(-1). Anthraquinones solubility in pressurized hot water was determined. The results indicate a presence of a mass transfer limitation in the extraction process from solid matrix.