This article describes the structural stabilities of [2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6- dichloro-3-sulfonatophenyl)porphinato] manganese(III) X (where X = H2O and/or OH-, depending on pH) (MnTDCSPPBr8) and [2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetra(4-sulfonatophenyl)porphinato] manganese(III) X (where X = H2O and/or OH-, depending on pH) (MnTSPPBr8) toward H2O2 and NaOCl at various pH's, I = 0.2 M and 30 degreesC. In addition, the structural stabilities of these manganese porphyrins were investigated when they were bound to quaternary ammonium containing supports, namely, hexadecyltrimethylammonium bromide (CTAB), 2,6-ionene, 2,10-ionene and a poly[(vinylbenzyl)trimethylammonium chloride] latex, In alkaline media, both manganese porphyrins degraded and precipitated even in the absence of both of the oxidants. In neutral and acidic solutions, they showed increasing stabilities toward H2O2 as pH decreased and almost no stabilities toward NaOCl. When bound to CTAB and the latex, they gained very high stabilities toward H2O2 at pH < 2 and almost no degradation was observed. On the other hand, the stabilities of the ionene-bound manganese porphyrins were close to the free complexes. The pseudo-first order degradation rate constants of MnTDCSPPBr8, MnTSPPBr8 and their supported analogues were determined.