A method of approximate output tracking for a class of causal nonminimum-phase multiple-input-multiple-output (MIMO) systems with nonlinear time-varying uncertainties and unmeasurable disturbances is considered. The nomninimum-phase output-tracking problem is transformed into a state-tracking problem. The presented technique employs linear algebraic methods and internal model principle. Sliding mode control approach is used in the example to illustrate a complete constructive algorithm.