We experimentally demonstrate cavity field control by another laser beam with three-level ⌳-type atoms inside an optical ring cavity. By adjusting the frequency detuning of the controlling beam ͑coupled to one of the atomic transitions͒, the intensity of the cavity field interacting with another atomic transition is switched on and off. Such all-optical switching between two steady states is caused by the enhanced Kerr nonlinearity due to atomic coherence in such system.