The fragmentation behavior of a series of diterpene quinones related. to tanshinone, isolated from Salvia miltiorrhixa Bunge, Salvia pwzewalskii Mazim, Var. mandarinorum Stib, and Salvia trijuga Diels, vvas studied by low and high resolution mass spectrometry. The general fragmentation pathways of these compounds were proposed. An unusual loss of ozygen atom directly from the molecular ion was observed in oases of some hydroxy-substituted analogs. A comparison of the spectra of przewaquinone B(2)and hydrozytanshinoneⅡ-A(7)with those of their derivatives, such as acetates (3,6) and quinoxalines (13, 14), oougled with high resolution data and metastable measurement by defoonsing technique, allowed us to postulate that the ozygen lost originates from the hydrozyl group as a result of intramoleoular group interaction with the neighboring quinone functionality.