The reaction of nitrite ion with ascorbic acid and its effect on the rate of nitrosation of secondary amines have been investigated by differential pulse polarography in aqueous acidic solution. Ascorbic acid shows nonuniform behavior: it accelerates the nitrosation of N-methylaniline between pH 1.00 and 1.95, allows the nitrosation of diphenylamine and iminodiacetonitrile, but inhibits the nitrosation of secondary amines, such as dimethylamine, diethylamine, proline, hydroxyproline, N-methylaminoacetonitrile, N-methylaminopropionitrile, and sarcosine. The nitrosating agent generated by the reaction between ascorbic acid and nitrite ion appears to be oxyhyponitrite ion (N2O3-2).