An asymmetric PI (aPI) controller based on a control algorithm, which is the modification of the PI control method, has been suggested. The principal characteristic feature of the aPI controller is that different values of proportional and integral constants are used at positive and at negative errors. Contrary to the classical PI controller, the proposed controller allows us to improve the positive disturbance rejection of control systems without sacrificing the unit step response dynamics. Results of the investigation of the concrete control systems based on the aPI controller are also presented. Using the dynamic system simulation program Simulink performed the investigation.