Undrained cyclic triaxial and bender element tests were performed on sand and sand-silt mixtures for the investigation of the effect of nonplastic fines on the relationship between liquefaction resistance and shear wave velocity. The results show that this relationship depends on factors, such as fines content, density and confining effective stress. Based on the above results, field liquefaction resistance and overburden stress corrected shear wave velocity curves for sands containing nonplastic fines are derived and compared to other previously proposed curves and in particular the recommended in the semi-empirical procedure by Andrus and Stokoe. The results indicate that the limiting upper value of the overburden stress-corrected shear wave velocity may be higher for sands and considerably lower for sands containing nonplastic fines than the corresponding values, suggested in the semi-empirical procedure.