The nuclear magnetic resonance and mass spectral behavior of 5-phenyltetrazole, 5-p-nitrophenyl-tetrazole and the 1-methyl and 2-methyl derivatives of each have been determined. Characteristic differences between the spectra of the 1-methyl and 2-methyl isomers have been noted and found to be useful for the purpose of structural assignments. The synthesis of 1- and 2-methyl-5-phenyltetrazole containing 47.5 % of15N in the 1- and 4-positions of the tetrazole ring aided interpretation of the mass spectra and also allowed measurement of a geminal and a vicinal15N—H coupling constant.