Ultrasonic techniques show great promise for nondestructive characterization of high temperature composites which are usually manufactured with specially designed fiber-matrix interphases. Ultrasonically measured composite elastic moduli are important mechanical characteristics, and the problem of interphase characterization is also often related to the measured composite moduli. The characterization of interphase is critical since the interphase transfers load from the fiber to the matrix and its properties significantly affects the overall mechanical performance of the composite. Chu and Rokhlin have recently developed methods to determine fiber-matrix interphase elastic properties from ultrasonically measured composite moduli using static micromechanical models [1, 2, 3, 4]. Since their method is based on measurements of ultrasonic wave velocities in different directions in the composite and on relating them to the static composite elastic moduli, error may be introduced in determining the static composite moduli from wave velocity data if dispersion is not negligible. We have performed experimental measurements and theoretical studies of dispersion and attenuation for waves propagating along and normal to fibers in a SiC/Ti unidirectional metal matrix composite [5, 6, 7]. In this paper we focus on the effect of fiber-induced dispersion on determination of the composite and fiber-matrix interphase moduli.