The relations between the content of MTBE in gasoline and the detection frequency of MTBE in ground and surface water were analyzed using the percent by volume of MTBE in gasoline provided by NIPER. For groundwater, 21 metropolitan areas had information on detection frequency and percent volume of MTBE in gasoline, while for surface water, only 9 metropolitan areas had this information. For groundwater, three cities, i.e., Columbia, SC, Harrisburg, PA, and Norfolk, VA, had values of MTBE in gasoline for only 2 sampling periods and had a MTBE in gasoline for only 2 sampling periods. The frequency of detection of MTBE in surface and ground water had a positive relation to content of MTBE in gasoline. The occurrence of the fuel additive MTBE in ground and surface water was related to its issue in gasoline. The frequency of detection of MTBE was higher in areas that use greater amounts of MTBE in gasoline. As the percent by volume of MTBE in gasoline increased, the frequency of detection of MTBE in ground and surface water increased.