It is widely known that the seismic response characteristics of a soil site depends heavily on several key dynamicproperties of the soil stratum,such as predominant frequency and damping ratio.A widely used method for estimating thepredominant frequency of a soil site by using microtremor records,proposed by Nakamura,is investigated to determine itseffectiveness in estimating the damping ratio.The authors conducted some microtremor measurements of soil sites in HongKong and found that Nakamura’s method might also be used to estimate the damping ratio of a soil site.Damping ratio datafrom several typical soil sites were obtained from both Nakamura’s ratio curves using the half power point method and resonantcolumn tests.Regression analysis indicates that there is a strong correlation between the damping ratios derived from thesetwo different approaches. It is widely known that the seismic response characteristics of a soil site depends heavily on several key dynamic properties of the soil stratum, such as predominant frequency and damping ratio. A widely used method for estimating the predominant frequency of a soil site by using microtremor records, proposed by Nakamura, is investigated to determine itseffectiveness in estimating the damping ratio. The authors conducted a microtremor measurements of soil sites in HongKong and found that Nakamura’s method might also be used to estimate the damping ratio of a soil site. Damping ratio data from several typical soil sites were obtained from both Nakamura’s ratio curves using the half power point method and resonantcolumn tests. Regression analysis indicates that there is a strong correlation between the damping ratios derived from thesetwo different approaches.