Abstract: Well water samples were collected during the period of 1997 to 2009 from seventeen wells to represent Saq aquifer, Qassim Region, Kingdom of Saudi Arabia. The water samples were analyzed to determine their quality for domestic use. The water samples were investigated with respect to Electrical Conductivity (EC), total water hardness and the concentrations of hydrogen (pH), calcium (Ca2+), magnesium (Mg2+), chloride (Cl¯), sulfate SO2-4, nitrate NO∼3, fluoride (F¯) and ammonium NH+4. The electrical conductivity increased slowly with time from 1.18 to 1.39 dS m-1, with a mean of 1.31 dS m-1 for all water samples examined. The mean EC complies with the maximum permissible drinking water limits set by the local and international standards. The total hardness for the studied well water is 278.26 ppm as calcium carbonate which was classified as very hard water. Therefore, the water of wells should be softened to react with soap for domestic use. The pH in all water samples ranged from 6.77 to 7.28 with a mean of 7.02. This mean of pH complies well with standard value set for drinking water. The concentrations of the cations and anions follow, more or less, a trend similar to EC with time. The cations (Ca2+ and Mg2+) and the anions concentrations were lower than the maximum permissible drinking water limits. The concentrations of F¯ in the all of colleted samples ranged from 0.29-0.37 ppm with a mean of 0.36 ppm. The mean concentration of F¯ is alarming because it is below the lower permissible limit of 0.6 ppm set by the World Health Organization. So, the water of these wells must be fluorinated before drinking use. The concentration of in all water samples ranged between 0.0 to 0.27 ppm with a mean of 0.22 ppm. In general, the concentration of is alarming because it is higher than the permissible concentration in the drinking water (0.0 ppm).