This study has been conducted to evaluate the effect of different levels of nitrogen on nitrate reductase activity, nitrate content and vegetative growth (based on shoot and root dry weight) in selected Iranian land races of spinach. The experiment ws carried out in 2010-2011 as factorial design under randomize complete blocks in Agriculture College of Shahid Chamran University of Ahvaz. Seedlings of 10 land races of spinach were subjected to three nitrogen treatments (modified Hoagland solution with recommended level of KNO3 as control, Hoagland solution with two or three- fold level of KNO3). Results showed that nitrate reductase activity in leaves of ‘Gorgan’ and ‘Kerman’ land races were higher than other land races. In leaves of ‘Tonekabon’, ‘Zanjan-1’, ‘Sari-1’, ‘Sari-2’, ‘Khoor Abad- Qom’, nitrate reductase activitywere lower than other land races. Nitrate reductase activity at control (1 M KNO3) and two or three fold KNO3 level were significantly different in roots all land races.There was significant differences in root or shoot nitrate accumulation among the plants of all land races treated with different concentrations of KNO3.When grown under control or KNO3 treatment (2 M), plants of ‘Gorgan’ had the highest content of nitrate in shoot followed by plants of ‘Sari-1’ and ‘Saqri-2’ treated with KNO3 (3M). The results ofpresent study demonstrate that increasing nitrogen is highly effective in the metabolism of nitrate in roots and leaves of Iranian spinach land races. These differences may be important for selecting of a spinach land race as an efficient genotype for nitrate metabolism.