The reactions of peroxonitrite with the nucleophiles CN–, I–, and SCN– have been studied in alkali. Oxygen-atom transfer occurs from peroxonitrite to the nucleophile, with the production of nitrite. The reaction with cyanide is independent of pH, but that with iodide is subject to acid catalysis, indicating that peroxonitrous acid is the reacting species. These results are used for a comparison of peroxonitrite with other peroxides. The metal-ion catalysed self decomposition of peroxonitrite and the metal-ion catalysed reaction with peroxide also led to the production of nitrite. Mechanisms are suggested for these reactions.