The effect of the N/C (Nitrogen/Carbon (weight/weight)) ratio on the behavior of nitrogen in biomass liquefaction was examined. Cellulose and ammonia were selected as the simplest carbon and nitrogen sources, respectively. After reaction at 300 degrees C for 1 h, the reaction mixture was separated into oil-A (water soluble), oil-B (water insoluble), aqueous phase and residue. Both the yield and nitrogen content of the total oil (oil-A + oil-B) increased with increasing N/C ratio. On the other hand, the yield of residue decreased with increasing N/C ratio. These results show that ammonia acts both as a reactant and as a basic catalyst during the liquefaction of ammonia and cellulose. Distribution of nitrogen in the total oil showed the highest value (25.0%) at 0.18 N/C ratio and was small in the range of low N/C ratio. In the aqueous phase, soluble forms of organic nitrogen are recognized, while ammonia nitrogen increased with increasing N/C ratio. Distribution of nitrogen into the residue decreased with increasing N/C ratio. In the obtained oil, more than 60 compounds were detected by GC-MS. We identified 14 nitrogen-containing compounds, which were partly aromatic compounds. The liquefaction of cellulose and ammonia consisted of a very complicated combination of various reactions.