This paper discusses the robustL2-gain performance synthesis problem for a class of nonlinear uncertain systems. It is shown that the Riccati equation approach toH∞robust performance synthesis can be extended to solve this problem. Based on a positive definite solution of a Riccati inequality, a sufficient condition is given such that the nonlinear uncertain system is robust stable and itsL2gain is less than one. Using this condition, a state feedback law which ensures robustL2-gain performance of the closed-loop system is derived. The state feedback law is equivalent to the solution of anH∞standard design problem for an extended plant parametrized by scaling parameters. Finally, a design example and simulation results are given.