Pyrolysis of silanes, difluorosilane, and their mixtures has been observed by mass spectroscopy under isothermal conditions. The rates of SiH4 pyrolysis show a large compensation effect at low pressure, which agrees with the theory of unimolecular reaction. The pyrolysis rates of difluorosilane and silanes are enhanced synergistically when they are mixed together. The reaction mechanism proposed in this study for pyrolysis of the Si-containing species explains the observed experimental results well.