Technique of adaptive control of a multivariable plant in the presence of a bounded polyharmonics disturbance with infinity number of harmonic and the unknown amplitudes and frequencies is proposed. Control aim is a provision of a prescribed tolerances on plant and controller outputs forced vibrations. Adaptation process is based on finite-frequency identification of the plant and closed-loop system. Adaptation is ended when coeficients of the identified plant with controller and the identified closed-loop system are approximate. Conditions of adaptation convergence, which may be examined by experiment, are derived.