The regional aquifer system, the hydrogeological condition and salinity hazards in the middle part of Yamuna river sub-basin were investigated. Locally there occurs two to three tier aquifer system, but on a regional scale a single aquifer system down to depth of 100 m can be visualized. The sediments forming the aquifers are medium to coarse grained sands and gravels with thin layers of clay beds. In general the groundwater flow is towards east and southeast with some variation. Groundwater troughs have been developed at many places due to excessive groundwater withdrawal. There is wide spatial variation in the salinity of groundwater as evident from wide range of electrical conductivity (E.C.) values (500-6700 µS/cm). Large scale practice of dumping solid industrial wastes in the open field, utilization of canal and river water containing effluents of industries for irrigational purpose may be responsible for some increase in the salinity of groundwater in the study area, where natural processes are mainly responsible for the high salinity of the groundwater.