In Kuwait, as a lot of crude oil flowed out on the desert area, soil was contaminated by crude oil. As the rate of infiltration was very slow, groundwater was not directly contaminated by crude oil. However when rain water infiltrated into the contaminated soil, groundwater could bring oil into the aquifer. Therefore, the concentration of hydrocarbon in groundwater increased. The tracer test using chemical compositions and isotopes in ground water is useful for determining the origin and recharge time. The tracer test injecting tracer solution into an aquifer is useful for determining parameters in the aquifer. Therefore tracer tests will be used for analyzing oil contamination of soil and groundwater in Kuwait.