Electrospray ionization mass spectrometry is shown to offer excellent characterization of linear oligomeric polysulfides H(SC2H4OCH2OC2H4S)(n)H with n = 1-24. Analysis of the mass spectra reveals the presence of individual oligomers, the presence in certain oligomers of repeat units containing additional oxyalkylene groups (and in some cases a monosulfide link rather than disulfide) and the presence of end groups such as epoxy. The attachment of polyacrylates during cure can also be detected. Assignments of individual peaks can be confirmed by collision-induced decomposition and precursor ion experiments : the fragmentation pathways are relatively few except for linear polysulfides of complex structure. The best signal-to-noise conditions are achieved with low-to-medium cone voltages and a mobile phase of acetone containing 0.5% KI.