Volatile constituents of the defensive secretion of the stick insect,Megacrania tsudai Shiraki, in Taiwan have been analyzed by gas chromatography-mass spectrometry (GC-MS). In addition to the major component, actinidine, three more minor components of the secretion are identified as boschniakine and two stereoisomers of 1-acetyl-3-methylcyclopentane by comparing GC retention times with the authentic samples and synthetic compounds. Other components are also tentatively assigned as derivatives of actinidine.