We have reinvestigated the synthesis of 1-methyl-2,4,5-trinitroimidazole (MTNI; 1), and further characterized its physical properties. It is a promising candidate as an insensitive high explosive. Compound 1 was synthesized from the imidazole (2), via a 5-step sequence of reactions, and subjected to various sensitivity tests for explosives. The structure of 1 was characterized by X-ray diffraction. The crystal is orthorhombic; C 4 H 3 N 5 O 6 , M = 217.11, Z = 8, Pca2 1, a = 8.6183(6) Γ
, b = 17.7119(12) Γ
, c = 10.6873(7) Γ
, V = 1631.38(19) Γ
3 , Dc = 1.768 g/cm 3 . The structure was refined to R = 0.0284 for 3201 independent reflections with I > 2Ο(I). The molecular structures calculated by high levels of ab initio and density functional theories were in good agreement with those observed by X-ray experiment. According to our preliminary sensitivity tests, 1 was characterized to be intermediate in sensitivity between RDX and TNT. The explosive performances were evaluated theoretically, and were found to be comparable to those of RDX. In addition, owing to its low melting point (82 Β°C), 1 is believed to be an excellent candidate for inclusion in melt-castable explosives, and may lead to increased explosive power.