To study scale-effects on wave propagation in 3-D heterogeneous media, we conducted dynamic and static laboratory experiments on seven samples of glass beads cast with epoxy. We measured P and S wave velocities and frequency dispersion by the pulse-transmission method, and static elastic Young's modulus by a uniaxial stress test. We changed the scale of the heterogeneity by varying the diameter of the glass beads in each sample, and obtained wavelength to scale ratios varying from 0.2 to 20. We observed about 22% P-wave velocity dispersion and 15% S-wave velocity dispersion within this range of wavelength to scale ratios. We observed no scale effects on the static Young's modulus of the same seven samples. It is clear that strong wave velocity dispersion in the experiment is due to the dynamic wavelength-scale effects caused by scattering. ¿ American Geophysical Union 1995