For fuzzy-rule based feedback control systems, a stability condition in the form of an extension of the circle criterion was presented. Nonlinear characteristic of a fuzzy controller with two inputs and one output variables may be restricted in an extended form of the sector condition. This leads to an absolute stability condition (or input-output stability condition) in the frequency domain with a multiplier depending on the form of transfer functions before the fuzzy controller. The condition covers stability problems for many classes of practical fuzzy control systems. Two numerical examples are given.