The application of desorption and direct inlet with electron impact and chemical ionization mass spectrometry of some 2-chloroethyl phosphonates related to etephon is described. Comparison of these methods showed that there are highly useful for obtaining: 1) adduct ions, especially protonated molecular ions: chemical ionization. 2) significant fragment ions: methane and electron impact ionization. Interpretation of spectra, based on the considerable analogy between the different structures of the phosphonates is described in this work. A choice between EI and CI mass spectrometry with either direct inlet or desorption technics, depending on the volatility of the compounds and the purpose of analysis, is done. The low fragmentation obtained by ammonia chemical ionization was used to analyze different mixtures of phosphonates.