Polysulfide oligomers H(SC2H4OCH2OC2H4S)(n)H with n=1-24 can be characterized by electrospray ionization mass spectrometry. Samples prepared by the conventional method are shown to contain up to eight series of oligomers differing in structure by one of a small group of variants in one (or sometimes two) of the repeat units, e.g. with one less S atom or an additional CH2O group. The composition of individual ions can be confirmed by collision-induced decomposition of cationized polysulfides, which yields unambiguous spectra of the fragmented ions.