An integrated all-optical switch based on a high-Qnonlinear cylindrical microcavity resonator is proposed. The switch consists of single mode planar waveguides that allow coupling light in and out to a microresonator, exhibiting whispering gallery modes. Due to the highQfactor and the small dimensions, fast switching at low power is feasible for devices based on presently available nonlinear polymers as the active material. In this approach, the transmission of an integrated optical waveguide close to a microcavity has been measured and related to the resonances of the cylindrical microcavity. ©1997 American Institute of Physics.