The synthesis, NMR spectroscopic characterization and structure determination of highly explosive tetrazole azide, a very nitrogen-rich material (88.3% N) is reported. Tetrazole azide was prepared in high yield from the diazotation reaction of aminotetrazole, followed by treatment of the formed diazonium salt with sodium azide. Synthesis in diethylether/methanol and recrystallization from diethylether afforded colorless cubes: CHN7 (1): monoclinic, P1 2(1)/n(1), a = 1346.6(5), b = 499.6(2), c = 1360.9(5) pm, beta = 105.14(1)degrees, V = 0.884(2) nm(3), Z = 8, rho = 1.670 g cm(-3). The observed structural parameters (X-ray) are in good accordance with the results from molecular orbital (MO) calculations. The computed electrostatic potential (B3LYP) suggests a pronounced shock and friction sensitivity which was confirmed experimentally. Quantitative valence bond (VB) calculations were performed for the most important 21 VB structures in order to obtain the structural weights and to obtain an assessment for the importance of the various individual VB structures considered.