A new technique has been developed for analyzing the constant bottomhole pressure (BHP) test data. The method presented in this paper allows to calculate the skin factor for damaged and stimulated oil wells. Advantages of the BHP test are: (1) they do not require that the well be shut in; (2) the fluid production can be easily controlled (at constant flow rate tests the BHP is changing with time); and (3) wellbore storage effects on the test data are short-lived. It is assumed that the instantaneous flow rate and time data are available from a well produced against a constant bottomhole pressure. Only records of the flowing time and flow rate data are required to compute the value of the skin factor A semi theoretical equation is used to approximate the dimensionless flow rate. This formula is used to obtain a quadratic equation for determining the skin factor The accuracy of the basic quation will be shown below. The paper includes an example of calculation.