Nitrate  and  nitrite  in  drinking  water  is  harmful  for   human health,

   specialy when its amount is more than the standard  level.The purpose of

   this   study   include  measuring  concentration   of   nitrate  and  nitrite  in

   drinking water of  Hamadan city in each  season, during one year.

         In order to compare the seasonal nitrate and nitrite,totally 232 sample

   were taken from water. The  WHO standard methods was used to analysis

   the   nitrate and nitrite concentration in the water .

         The results  showed that concentration of nitrate and nitrite were 17.72

   and  0.03 mg/lit respectively, that were not more than  standard limit.  But

   the  concentration  of   nitrate  in  summer was more than  others seasons,

   and  the difference was statistically significant (P < 0.05 ) .

         Finally, at the present time,  it  can  be  concluded that, concern  with

   concentration  of  nitrate  and  nitrites  in  drinking  water  of  Hamadan, is

   healthy.