The article presents a new approach to History Matching of hydrocarbon reservoirs, and its successful application. In a conventional approach the static geological model is built first, containing also the wells and a certain kind of representation of the outer aquifer The model must be verified, i.e history matched by upscaling to a dynamic model and by comparing its result to the production history. If the comparison is successful, the model is suitable for forecasting and for evaluating future development scenarios. The simulator calculates the bottom hole pressures, gas oil ratio (GOR) and water cut (WC) over the entire production history. The reservoir model is modified, if these values do not match the measured ones. The new method does the opposite: the production and pressure data are fixed and the simulator decides under which conditions the fixed parameters could be met. The pressures, the GORs and WCs are data and not results. The calculation shows where and under which conditions the well could operate in the same manner as it really did and from where how much water must flow in. The name of this approach is Target Pressure and Phase Method, abbreviated TPPM. The article is presented in two consecutive issues of this journal. This issue concentrates on the idea, the TPPM workflow and a small example. The coming (December) issue completes the work with a full field application of TPPM.