The effects of some physical and chemical factors on callus growth and flavonoids formation in callus cultures of Saussurea medusa Maxim were studied. The optimal temperature for callus growth and flavonoids formation were 25 degrees C. Flavonoids formation were greatly inhibited under dark condition, and stimulated by white light. Callus growth was promoted when 1 mg/L NAA and 0.2 mg/L KT were added to the media. The combination of 5% sucrose and 1% glucose was useful for callus growth and flavonoids formation. A fine callus strain of S.medusa was selected through irradiation with 4000 Gy of gamma-ray. The growth rate and flavonoids content of the callus strain were high and stable. Sensitive and rapid methods of high-performance liquid chromatography as well as UV spectrophotometry were developed for detecting the flavonoids in cultured cells. The results revealed that the content of total flavonoids in dry cells under white light condition was 3.2%, 4.4 times more than under dark condition and the control of flavonoids in dry cell culture at 25 degrees C was 2.02% which was 5 and 3.2 times more than those cultured at 20 degrees C and 35 degrees C respectively.