Concentrations of nitrate and trace elements such as arsenic,cadmium,chromium,copper,manganese,nickel,lead,selenium,antimony and mercury in 18 different brands of bottled water were investigated.For comparison,samples of tap and well water from three different places of Tehran were also analyzed.UV/VIS spectrophotometer and Graphite Furnace Atomic Absorption Spectrometer were used for the analysis of nitrate and trace elements,respectively.Results obtained were compared to Iranian,World Health Organization(WHO)and Environmental Protection Agency(EPA)guideline for drinking water.Nitrate concentration in bottled,tap and well water samples were in maximum safe nitrate concentration of Iranian and WHO standards.However,70%of bottled water samples and one sample of tap water were below the standard level proposed by EPA and probably remedial action should be taken.Concentration levels of all analyzed elements investigated in all examined water samples were below the maximum contaminant level prescribed by Iranian,WHO and EPA regulations. Concentrations of nitrate and trace elements such as arsenic, cadmium, chromium, copper, manganese, nickel, lead, selenium, antimony and mercury were investigated in 18 different brands of bottled water were .For comparison, samples of tap and well water from three different places of Tehran were also analyzed. UV / VIS spectrophotometer and Graphite Furnace Atomic Absorption Spectrometer were used for the analysis of nitrate and trace elements, respectively. Results obtained were compared to Iranian, World Health Organization (WHO) and Environmental Protection Agency (EPA) guideline for drinking water. Nitrate concentration in bottled, tap and well water samples were in maximum safe nitrate concentration of Iranian and WHO standards. Yet, 70% of bottled water samples and one sample of tap water were below the standard level proposed by EPA and probably remedial action should be taken.Concentration levels of all analyzed elements investigated in all examined water samples were below the maximum contaminant leve l prescribed by Iranian, WHO and EPA regulations.