Abstract During a pressure drawdown test, it is quite difficult to hold a constant rate long enough to achieve the test requirements, especially for horizontal wells. Any change in rate, if not taken into account, can lead to erroneous results. Furthermore, pressure drawdown tests are not suitable in sand producing wells. Pressure buildup tests, in high production wells, are uneconomical because of income loss. For gas wells, it is impossible to determine both the coefficients of turbulence and the skin factor from a single constant rate test. For these reasons, a Multi-Rate test should be run instead of buildup or constant rate drawdown tests. A method is presented to analyze variable rate tests for oil reservoirs. In this study, it is proposed to plot first the pressure variation, Δp/Qn versus the flowing time, t, and in a Log-Log graph the principle of superposition is applied for each flow regime, taking into account the time interval of each flow period. This method is used to estimate the reservoir parameters such as the permeability and skin. The pressure derivative concept is introduced for interpreting multi-rate tests. Only two different parameters are needed from the graph, the slope and intercept. The slope is used to estimate the permeability, and the intercept yields the skin factor. The proposed technique is applicable for the interpretation of either continuously changing flow rate tests or a series of constant rate tests. This technique is illustrated by several numerical field examples for oil reservoirs.