Chlorine, which is widely used in the disinfection process of waters, forms trihalomethanes from disinfection by-products by entering into a reaction with natural organic substances in water resources. Control of trihalomethane (THM) formations is possible by the removal of substances that lead to these formation. In recent years Advance Oxidation Procedures are the preferred methods of treatment  for removing humic substances from the main THM precursors.The purpose of this study is; evaluation of the researches about the formation of THMs formed as a result of disinfection process in drinking water, health effects, differences between the practices applied in Turkey and the world and control methods and their advantages and disadvantages.  A limited number of scientific studies on the subject in our country, have been widely preferred due to the low cost of it is still widely preferred and the negative effects on the health of the formed byproducts constitute the most important reasons for the study. Key words:   Disinfection by Product, THM Precursors, Ozone, Hydrogen peroxide, , Advanced Oxidation Process, Humic Substances.