This paper presents a computer tool for tuning PID controllers. What makes this tool different to others available in the market is the ability to model the most important load disturbances. The MISO calculated model enables a better tuning of the PID loop, both for the servo and regulatory cases. This is of special interest in the Petrochemical Industry where most of the PID controllers have a fixed design criterion, either rejecting disturbances having a fixed setpoint, or following the setpoint, like in Multivariable Predictive Control applications, where the MPC controller is writing its output to the PID controllers setpoint. The tool is the major result of a joint industry-university development. The tool is being heavily used in all the refineries and some petrochemical complex of the REPSOL-YPF group.