The mathematical model for flow and temperature distribution for the water alternating gas (WAG) process had been developed. Water alternating gas (WAG) injection has been a popular method for commercial gas injection projects worldwide. The injection of water and gas alternatively offers better mobility control of gas and hence, improves the volumetric sweep efficiency. The model is generated for the injection well with one cycle of water and one cycle of injected gas. There are some considerations for the three phases modeling in this study. The scope of the model is to develop the flow model for cylindrical, gravity segregation, turbulency effect due to the high injection rate, incompressible water, slightly compressible oil, compressible gas, IMPES method and with ignoring the tangential flow. The energy balance equation for the three phases could be expanded after the saturations from the flow part had been obtained. These are the conditions for solving the equation for temperature distribution: Cylindrical, implicit method, convection and conduction with ignoring tangential temperature gradient. In order to solve the governing equations, an analytical method had been used for the two and three phase systems around the wellbore; then a program had developed to do the iteration for implicit parts. The water, gas and oil pressures and saturations had been obtained in addition with the system temperature for homogeneous and heterogeneous media. Copyright 2015, Society of Petroleum Engineers.