It is important to be aware of fluoride concentrations in drinking water and to ensure levels are adjusted to acceptable levels because if the levels are not within the suggested range as stated by the Ontario Drinking Water Standards, serious health complications may arise. Water from ten private homeowner wells was sampled for fluoride concentrations (amongst other parameters) and data was also used from the Provincial Groundwater Monitoring Network. These samples were all taken in different types of bedrock in Thunder Bay and the surrounding area which included: the Rove Formation, the Gunflint Formation, metasedimentary, diabase, massive granite, intermediate intrusive, mafic metavolcanic, and the Sibley Goup. There were four characteristics of the bedrock which were believed to have the biggest influence of fluoride concentration which were calcium concentration, pH levels, presence of fluorite, and depth of the well. Based on interpretation of my data and the available geological information, out of these four influences on the concentration of fluoride, it is likely that wells which are most susceptible to having high levels of fluoride are those which encounter fluorite mineralized vein systems. These systems are most common in areas underlain by the Rove and Gunflint Formations as well as diabase. However, this is a small data set and although it does seem like the Rove and Gunflint Formations as well as diabase most commonly have higher fluoride levels, it is still suggested that homeowners who use well water for drinking have it tested for regularly as reliable data should be based on a larger scale and during a longer time frame.