Summary: A new procedure of robust control design is presented for nonlinear systems with parametric uncertainty and disturbance. This nonlinear optimization-based approach can design robust nonlinear controllers of widely different structures and arbitrary complexity. By taking the worst-case design approach, a minimax optimization problem is formulated. A number of state-of-the-art optimization procedures are explored as possible candidates for minimaximization. It is determined that the tools of non-smooth analysis and optimization are the most useful for the efficient solution of practical size worst-case design problems. The controller designs produced by the minimax optimization algorithm are discussed and the performance of the controllers is studied by simulations.