Abstract: In order to investigate plant density and nitrogen fertilizer on nitrogen uptake from soil and nitrate pollution in potato tuber cu. Agria, a factorial experiment based on randomized complete block design with three replications was carried out in Ardabil, Iran, in 2006. Factors were nitrogen levels (0, 80, 160 and 200 kg ha-1 net nitrogen) and plant densities (5.5, 7.5 and 11 plant m-2). Results showed that the most nitrogen uptake by plant aerial parts and the most nitrate concentration in dry and fresh tuber weight were observed at 200 kg ha-1 nitrogen, 11 plant m-2 and 200 kg ha-1 nitrogen, 5.5 plant m-2, respectively. At 160 kg ha-1 nitrogen (as equal to 80 kg ha-1 nitrogen) and 11 plant m-2, the most tuber and yield of tuber were gained. With increasing nitrogen application up to 160 kg ha-1, nitrogen uptake by tuber, number of tuber, tuber dry weight and mean tuber weight was increased. 160 and 80 kg ha-1 nitrogen jointly with density of 5.5 plant m-2, caused the most mean tuber weight per plant. So, utilization of 80 kg ha-1 nitrogen to reach highest yield and less nitrate pollution, density of 11 plant m-2 to gain seed tuber (because of reduction in tuber weight and size) and density of 7.5 plant m-2 for eating usages, are recommended.