The dihydroxylamine radical anion (HNO2-., With the H atom on the nitrogen atom) is produced by the reaction of H atoms in the pulse radiolysis of nitrite solutions and decays in water with a rate constant of 5.0 x 10(3) s(-1). Its absorption spectrum has a maximum at 270 nm with molar absorptivity of 2.8 x 10(3) M-1 cm(-1). The decay of HNO2-. is catalyzed by both acids and bases. The hydronitrite radical (NO22-.) produced by the reaction of e(aq)(-) with nitrite exhibits no absorption spectrum between 270 and 550 nm. It is much shorter-lived than HNO2-., disappearing at 1.6 x 10(6) s(-1) without generating any HNO2-.. Neither radical species has any observable pK(a)'s, but the pK(a) for HNO2-. has been estimated to be lower than 9;3 from the rate data on the hydroxide-catalyzed decomposition of this radical. Both HNO2-. and NO22-. reduce methyl viologen, and the. reduction by HNO2-. has been used to measure its yield, which is found to be 0.63 radicals per 100 eV. Thus, the production of HNO2-. by H atoms is quantitative. Collectively, these data represent a major revision of. the reductive radiation chemistry of nitrite.