Determinations of volatile components of essential oil contained in Asiasari Radix were studied by head space gas chromatography. The head space gas, which was generated by heating 0.2 g of crude drug with 1.0 ml of water at 90 degrees C for 45 min, was analyzed directly by gas chromatography or gas chromatography-mass spectrometry. This method was rapid, and did not require tedious procedures and time consuming, and without contamination of the column.