Groundwater and river water samples were collected from the study area to investigate the spatial distribution of nitrate (NO3-) in the central-west region of Bangladesh. The shallow and deep groundwater nitrate concentrations ranged from <0.10 to 75.12 and <0.10 to 40.78mg/L, respectively. Major river water NO3- concentrations were ranged from 0.98 to 2.32 mg/L with an average of 1.8 mg/L The average Cl-/NO3- ratio (4.9) of major river water has been considered as reference point to delineate denitrification processes. The alluvial fan, alluvial, deltaic and coastal deposits shallow groundwater having Cl-/NO3- values less than that of the average river water value (4.9), suggested denitrification processes within the aquifers. On the other hand, denitrification processes are insignificant in the Pleistocene terraces area aquifers related to relatively higher concentrations of nitrate. Iron pyrite has been found as insignificant effect on denitrification. (C) 2008 Elsevier B.V. All rights reserved.