A method has been developed to measure, nondestructively, the dynamic modulus of an adhesive in the bond. The dynamic modulus, E, is defined as the stress-to-strain ratio for sinusoidal displacements, and can be expressed as E=E1−iE2, where E₁ is the ordinary Young's modulus and E₂ is the viscous modulus representing dynamic losses in the material. Nolle and Westervelt have derived formulas for E₁ and E₂ of a thin adhesive layer joining two cylindrical bars end-to-end. The relations require a knowledge of the resonance properties of the cemented bar and a continuous bar of the same length and material. The equipment for obtaining the necessary resonance properties, the resonant frequency and half-power bandwidth, consists of three major parts: a driving system to set up longitudinal ultrasonic vibrations in the specimens, a detecting system to indicate the amplitude of vibrations, and a frequency measuring system. Measurements have been made on stainless steel bar specimens, cemented with a phenol-formaldehyde polyvinyl-butyral adhesive, which have been subjected to various heat treatments. The results of this study indicate that the measured dynamic modulus is useful for selecting from a group of treated specimens those which have deteriorated and have low tensile strength. The method described is applicable to cemented-bar specimens composed of other types of bars and adhesives, provided that certain conditions pertaining to the derivation of the formulas for the moduli are met. There is a possibility that similar principles can be used to measure the dynamic modulus of reed type specimens composed of sections of lap joint or laminate.