Oxidation of 3,6-diamino-1,2,4,5-tetrazine (1) with most peracids gave 3,6-diamino-1,2,4,5-tetrazine 1,4-dioxide (3) as the major product; however, treatment of 1 with peroxytrifluoroacetic acid (PTFA) gave 3,6-diamino-1,2,4,5-tetrazine 1-oxide (4) as the major product along with a small amount of 3-amino-6-nitro-1,2,4,5-tetrazine 2,4-dioxide (5). Oxidation of 3,6-bis(S,S-dimethylsulfilimino)-1,2,4,5-tetrazine (6) with 3-chloroperoxybenzoic acid (MCPBA) gave 3-S,S-(dimethylsulfilimino)-6-nitroso-1,2,4,5-tetrazine (7), which was oxidized further with dimethyldioxirane to 3-(S,S-dimethylsulfoximino)-6-nitro-1,2,4,5-tetrazine (8). All attempts to obtain 3,6-dinitro-1,2,4,5-tetrazine (2) by further oxidation of 7 or 8 failed.