Abstarct: Tracing is one of the most precise and reliable methods in hydrogeology. It is an important task to select a proper tracer. To achieve this aim, it is necessary to have enough knowledge of the physical and chemical behaviors of various tracers in different field conditions. In this research, the effect of environmental factors such as pH, sunlight, temperature, salinity, time on different tracers as well as adsorption of tracers onto porous media are discussed. Also, the impacts of artificial factors such as free color, hydrocarbon pollutants and mixing on a number of common tracers that are currently in use in Iran are evaluated. Different categories of tracers such as Uranine, Eosin and RhodamineB (Fluorescent tracers), NaCl and KCl (Chemical tracers) and KMnO4 (Non fluorescent dye tracer) have been selected for this study. The result of the experiments show that Uranine losses its florescence in acid environments, while in alkaline condition its florescence increases. The results also show that because of photochemical decay, Eosin is the most unstable tracer if subjected to sun light. KMnO4 turn to brown under sun light and higher temperature conditions and may lose its tracing capability. The fluorescence intensity of RhodamineB decreases whit increasing temperature and NaCl and KCl induced salinity. Uranine and Eosin have high resistance against high temperature and salinity. An important factor in ground water tracing is tracer adsorption in porous media environment. RhodamineB is a cationic tracer and is easily adsorbed. Uranine and Eosin have high resistance to adsorbing. KMnO4 is adsorbed easily. Chlorine used in drinking water treatment facilitues is a strong oxidizer even in low concentration. It can lead to elimination of fluorescence of both Uranine, Eosin and RhodmineB. Experiments regarding common hydrocarbon pollutants in groundwater show that the color intensity of KMnO4 increases when percentage of oil are increased. However, presence of oil doesn't change fluorescence of Uranine, Eosin and RhodamineB. Also KMnO4 causes these tracers to decay. Therefore simultaneous application of these tracers is not recommended.