In the present study, the effects of nitrogen supply (low nitrogen: LN and high nitrogen: HN) on As stress (25 mu M) responses of rice seedlings were monitored for 7 d. The mean length of primary, adventitious and lateral roots and number of adventitious and lateral roots were significantly improved in LN + As, while further reduced in HN + As, as compared to As alone treatment at 7 d. The LN + As treatment resulted in significant decline in As (848 mu g g(-1) DW) than that in As alone treatment (1434 mu g g(-1) DW) in roots but no significant effect was seen in shoot. In contrast, HN + As treatment showed significant increase in shoot As (6.86 mu g g(-1) DW) as compared to As alone treatment (3.43 mu g g(-1) DW). The level of nitrate was increased in roots but declined in shoots in As alone treatment. Surprisingly, no improvement in nitrate level was seen in HN + As as compared to that in As alone treatment in both root and shoot. The expression analysis of nitrate transporters (NRT2;1, NRT2;3a, NRT2;4) showed significant differences in expression patterns in As, LN + As and HN + As treatments. In conclusion, nitrogen supply had profound influences on responses of rice plants to As.