Abstract Surface ionization mass spectrometry was performed on 14 organosilicon compounds, by use of a quadrupole mass spectrometer in which the thermionic ion source was a rhenium oxide emitter. The data provide the first measurement of the surface ionization mass spectra of these compounds. The results are interpreted in terms of the modes of ion formation. Almost all the ion-current is carried by metal-containing ions except for the organosilicons having amino groups. In general the most favored ionization processes, which are shown to be directly related to the ionization energy, are those which give even-electron ions. Some of the mass spectra of the examined silicon compounds are compared with those of the analogous hydrocarbons. In order to explain the spectra of tetraethylsilane and triethylsilane, the ionization energy of the (C 2H 5) 3Si radical was calculated by the STO-3G method of the Gaussian-80H programs.