Object To study the volatile constituents in the TCM preparation "Pao Chai Pill" made in Yangcheng (Guangzhou) (YPCP) in comparison with that made in Hongkong (HPCP) to gain some insight for the renewal of YPCP to a new dosage form Methods The volatile constituents were extracted with the aid of ultrasonic wave in organic solvent, and identified by GC-MS and elucidated on the standard MS data Their relative contents in percentage were calculated by area normalization Results 24 and 20 volatile constituents were identified in YPCP and HPCP respectively Conclusion YPCP showed more rich in sesquiterpene lactones but less sesquiterpenes and sesquiterpene alcohols than HPCP