(E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ) is formed from the oxidation of the unsymmetrical 1,1-dimethylhydrazine (UDMH) and is used as a storable liquid fuel which can be considered as a new potential propellant for space rocket propulsion. To better understand the toxicological behavior of the compound, an intraperitoneal administration of TMTZ was performed in mice to define its toxicokinetics and tissue distribution. A fully validated liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) assay was developed to determine TMTZ levels in biological samples. Determination of TMTZ was achieved using 50 μL of plasma or tissue solution. Precipitation with ammonium sulfate and acetonitrile was used for sample preparation. Liquid chromatography was performed on an Atlantis HILIC Silica column (Waters; 3 μm, 150 mm × 2.1 mm i.d.). Isocratic elution with a mixture of ammonium acetate buffer (pH 5, 100 mM)/water/acetonitrile (3:2:95, v/v/v) was used. The detection was conducted using an electrospray source in positive ion mode. TMTZ and (15)N2-TMTZ (internal standard) were quantitated in selected reaction monitoring mode using the transition m/z 117→72 and 119→74, respectively. Standard curves exhibited excellent linearity in the range of 10-500 ng/mL for plasma and 50-2000 ng/mL for all tissues (heart, liver, brain, kidney, and lung) analyzed, and acceptable precision and accuracy (<10 %) were obtained. The elimination rate constant strongly suggests that TMTZ was very quickly eliminated from the body. The results of tissue distribution experiments indicated that TMTZ underwent a rapid distribution into limited organs such as the liver, kidney, and brain.