An approximate theory of rod vibration given Love has been extended to describe the occurrence of wave effects, or wave resonances, in rubber antivibration mountings. Thus, the longitudinal vibration of a mass‐loaded rubber mount of significant lateral dimensions and uniform cross section has been determined with the assumption that the elastic modulus and damping factor of the rubber are frequency‐ dependent quantities. Knowledge of the manner in which the elastic modulus and damping factor of natural rubber, natural rubber filled with carbon black, and a high‐damping synthetic rubber depend upon frequency has enabled realistic computations of transmissibility to be made. These computations have been contrasted with results obtained, for the same rubbers, from the simple one‐degree‐of‐freedom theory in which the occurrence of wave effects is disregarded. The effectiveness of the natural‐rubber mountings, which have relatively small clamping, is overestimated by the simple theory at high frequencies, although transmissibility will normally remain a small quantity. In the case of the high‐damping rubber considered, the results of the simple and Love theories are in relatively close agreement.