Four distinct pathways of unimolecular decomposition of nitroethylene, the C-NO2 bond breaking, nitroto-nitrite rearrangement, 1,2-elimination reaction and 1,1-elimination reaction, have been computationally investigated with ab initio, MP2, MP4, and G2 methods as well as with DFT methods, The nitro-to-nitrite rearrangement and 1,2-elimination reaction ate found to give the lowest energy decomposition pathways for this molecule, about 15 kcal/mol lower than the cleavage of the nitro group.