This paper presents a study on the effect of non-linearities of an elastomeric bearing on isolated lag dynamics and coupled rotor/fuselage ground resonance stability of an idealized bearingless rotor blade. The rotor blade is modelled as an elastic beam with a non-linear elastomer and a rigid torque tube. First, amplitude dependent natural frequency of the blade in lag mode is analysed using numerical perturbation technique. Then the problem of amplitude-dependent stability of the coupled rotor/fuselage system under ground resonance condition is investigated. The results of the study indicate that the effect of amplitude seems to be more dominant on the progressive lag mode damping than on regressive lag mode damping. It is also observed that so far as the stability in ground resonance is concerned, there exists optimum locations for the attachment of both the elastomer and torque tube. ©2000 The American Institute of Aeronautics and Astronautics Inc. All rights reserved.