Fluoride (F - ) is an essential element for some animals having positive impact on their growth rate at even low levels. This element reduces the solubility of tooth enamel under acidic conditions. Concentration of fluoride higher than threshold level is harmful for humans and animals. In most arid and semiarid regions, groundwater is the main source of drinking and agricultural use. The objective of this study was to determine temporal and spatial variability of fluoride in groundwater in agricultural and industrial regions in a selected area in Markazi Province. Arak Plain is located in an arid to semiarid region in Markazi Province where the use of groundwater has become very important due to the drought crisis in recent years. The study region, with an area of about 25 km 2 , is located in the north and the west of Arak city. Water samples were randomly collected from wells during autumn and spring seasons. Also 30 composite surface soil samples (0-10 cm) were randomly taken. About 80 water samples were taken from wells in fall and 92 samples in spring. Soil pH, Electrical conductivity (ECe) and soil texture were measured. Fluoride in soil solution and water samples was measured by Ion Selective Electrode (ISE). The groundwater sampling location was determined using a GPA and land use of each sampling location was recorded. Water samples were analyzed for F - . NO 3 - , EC, pH, Cl - , K + , Na + ، Ca 2+ ، Mg 2+ ، SO 4 2- . The Fluoride concentration was mapped using Surfer computer program and kriging technique. Omnidirectional variograms were prepared for soil and groundwater fluoride concentration. Spherical model was the best model to describe spatial variability of most parameters. Mean square estimation error (MSEE), mean estimation error (MEE) and correlation coefficient were used to determine validation of the variograms. The results indicated that fluoride concentration in soil was higher in industrial areas as compared to that in agricultural soils. The difference in fluoride concentration in soils of industrial and agricultural areas was statistically significant. Average fluoride concentration in groundwater samples during two seasons ranged from 0.03 to 0.53 mg/l which is below the standard level (1.5 mg/l). The fluoride concentration was assessed to be suitable for irrigation and deficient for drinking. The concentration of fluoride was not significantly different among different land uses. However, the concentration of fluoride in groundwater samples was significantly different between two sampling periods. A significant correlation was obtained between the concentration of fluoride in soil solution and soil calcium carbonates and pH. Also, fluoride in water samples was highly correlated w