A possible new route for NO formation in hydrogen combustion is explored. The reaction sequence that converts molecular nitrogen into nitrogen oxides involves sequential recombination of N-2 with H atoms: N-2-->NNH-->N2H2-->N2H3. N-N bond cleavage occurs in the reaction of N2H3 with H-2 forming NH3 and NH2. These last species are oxidized mainly in the sequence NH3-->NH2-->NH-->N-->NO. Key reactions of the N2H3 formation and consumption as well as other important reactions revealed by sensitivity analysis and reaction path analysis are examined and discussed. Kinetic modeling of hydrogen combustion in stirred reactors demonstrates that this mechanism can be of importance in rich mixtures at relatively low temperatures (below about 1500 K) when other routes of NO formation are suppressed. Available measurements of NO formation in hydrogen combustion in stirred reactors have been modeled and analyzed. They neither confirm nor contradict the proposed route forming NO via N2H3. because these experiments have been conducted outside the range of conditions where this route is manifested.