Knowledge of shear-wave velocity structure, when used with compressional-wave velocity, can help constrain interpretations of composition from seismic refraction results. We present shear-velocity (vs) models from high-quality S-wave data from Southwest Germany, which combine with existing P-wave velocity (vp) models to give Poisson's ratio in the crust and uppermost mantle. In general, Poisson's ratio is 0.25 in the uppermost crust, 0.22--0.23 in the mid-crust, and varies laterally from 0.24--0.30 in the lower crust; the average Poisson's ratio for the whole crust is everywhere about 0.25. The laminated signature of the lower crust prominent on reflection on P-wave refraction data is absent on the S-wave refraction data, suggesting strong vertical variations of Poisson's ratio within the lower crust. No shear-wave refractions from the upper mantle are present, even where strong P-wave refractions are observed, possibly indicating an increase of Poisson's ratio with depth in the upper mantle. We interpret these results to indicate a high quartz content or fluid phases at low pore pressure in the mid-crust, a high feldspar content in the lower crust, and an increase in depletion of basaltic components with depth in the upper mantle. ¿ American Geophysical Union 1987