Nitrite in drinking water is a significant health concern. Oxidation of nitrite to nitrate in drinking water chlorination and chloramination was studied by jar tests. Results indicate that chlorination could cause oxidation of nitrite but not ammonia under the typical drinking water treatment conditions (i.e., >0.3 Mg Cl-2/L residual chlorine and near neutral pH). In chloramination, nitrite oxidation increased with the decreases of pH, the increases of Cl-2:N weight ratio and residual chlorine concentration, and was barely affected by contact time longer than 30 min. It was also observed that nitrite oxidation in chloramination was mainly controlled by Cl-2:N ratio, and a high Cl-2:N ratio of 6:1 could ensure significant nitrite oxidation under various conditions. The relationship between HClO concentration and nitrite oxidation indicates that nitrite oxidation was brought by reaction with HClO in chlorination, but primarily by reaction with monochloramine in chloramination, consistent with the reaction mechanisms reported in literature. These findings suggest that nitrite levels in drinking water can be effectively controlled by conventional chlorination and chloramination treatments. (C) 2007 Elsevier B.V. All rights reserved.