Nonlinear output tracking in multi-input/multi-output (MIMO) systems with unmatched nonlinearities and disturbances is considered in sliding modes, The system is nonlinearly transformed to a form convenient for sliding mode synthesis. Both conventional and dynamic sliding mode controllers are designed to provide the desired nonlinear output tracking, In both cases, only the time-dependent part of the unmatched disturbance must be estimated, An example is provided to demonstrate the new design approach. Results show that both conventional and dynamic sliding mode control are insensitive to matched disturbances, but that dynamic sliding mode control accommodates to unmatched disturbances.