Reaction of ethylene oxide with 1-alkyl- or 1-aryl-1,4-dihydrotetrazole-5-thiones in AcOH afforded the corresponding mesoionic (hydroxyethyl)tetrazoliumolates I [R = (CH2)2OH, Me (II), Ph]. The x-ray structure of II is presented. The reaction of tetrazolinones with Cl(CH2)2OH in the presence of KOH afforded a mixt. of the corresponding 1,3- and 1,4-disubstituted isomers. The isomers were characterized by their IR, 1H, 13C NMR, and mass spectra.