An attempt was made to estimate dynamic soil properties from strong-motion accelerograms recorded only at the ground surface. Spectrum and multiple-reflection analyses on the records could permit an evaluation of strain-dependent shear moduli and even damping factors in some cases, assuming that the soil profile at the recorded site is relatively simple. The analyses conducted on several sites indicated that : (1) the first predominant period of surface soil increases and the shape of the spectrum becomes less sharp, as the intensity of earthquake ground motion gets large, (2) the strain-dependent soil properties evaluated from strong-motion records are in fairly good agreement with those measured in the laboratory in a strain range from 10^<-5> to 10^<-2>, (3) the shear modulus ratio is better correlated with peak ground velocity than with peak ground acceleration, and (4) the maximum shear strain developed in the soil is uniquely correlated with peak ground velocity irrespective of site geological conditions.