The two-step Internal Model Control procedure is used for the synthesis of robust controllers for multivariable open-loop stable or unstable plants. In the first step the controller is designed so that the Integral Squared Error (ISE) is minimized for every external input (setpoint or output disturbance) direction in a set and their linear combinations. In the second step a low-pass filter is designed so that stability and good performance characteristics are maintained in the presence of model-plant mismatch. The problem is formulated as a minimization of the Structured Singular Value (SSV) for robust performance over the filter parameters.