Laboratory and field measurements of the small-strain shear modulus of a Piedmont residual soil were compared to gain a better understanding of mechanisms affecting stiffness. Resonant column tests were performed to study influences of void ratio, overconsolidation ratio, plasticity, confining stress, and degree of weathering. In-situ test results showed effects of increased confining stress with depth, and OCR, mass density, and void ratio were estimated using correlations to assess current in-situ state. In-situ measurements of low-amplitude shear moduli from seismic piezocones, seismic flat dilatometers, SASW, and crosshole tests were found to be in good agreement with laboratory values using the resonant column.