Disulfide bond was cleaved by a catalytic amount of nitric oxide in the presence of oxyge, which was confirmed by experiments employing two symmetrical disulfides. The reaction resulted in the formation of unsym-metrical disulfides in nearly 50% yields. The steric hindrance of alkyl disulfide slowed the reaction rate, and an electron-donating group on the aryl disulfide promoted the reaction. The substituent and S-nitrosothiol effects suggested that the reaction was initialized with an oxidative process by NO⁺.