The reaction between chlorite and formamidinesulfinic acid has been studied in perchloric acid between pH 1 and 3. The stoichiometry of the reaction in excess chlorite is HO2SC(NH)NH2 + ClO2- + H2O --> SO42- OC(NH2)(2) + Cl- + 2H(+) (A), while the stoichiometry in excess formamidinesulfinic acid is a mixture of (A) and (B) : 2HO(2)SC(NH)NH2 + ClO2- --> 2HO(3)SC(NH)NH2 + Cl- (B). In excess chlorite at the end of the oxidation of formamidinesulfinic acid ClO2 is formed from the reaction 2 ClO2- + HOCl + H+ --> 2ClO(2) + Cl- + H2O. The formation of ClO2 shows some oligooscillatory behavior in which, even in excess formamidinesulfinic acid, there is transient formation of ClO2. The reaction is autocatalytic in HOCl via the asymmetric Cl2O2 intermediate. The dynamics of the reaction are explained via a mechanism which is derived from the one used for the chlorite-thiourea reaction.