In this study, the nonlinear aeroelastic analyses of a wing with oscillating control surface have been performed in transonic flow regime. Nonlinear limit cycle oscillations concerned with aileron buzz phenomena have been examined using non-linear coupled-time integration method (CTIM) that include the numerical techniques of computational fluid dynamics and computational structural dynamics. The computed results are compared with those of clean wing model to show the effect of oscillating control surface. Especially, it is shown that the oscillation of control surface due to strong shock motions can lead to severe unstable vibrations of wing structure in the transonic flow region.