ABSTRACT The possibility of evaluating undrained cyclic strength of natural gravelly deposits using shear moduli was investigated. Through this study, the following conclusions were drawn. 1) It was found that cyclic shear moduli at relatively large strain amplitude were closely related with undrained cyclic strengths, irrespective of the effective confining pressure, grain size distributions and whether or not the samples are intact, whereas there seems to no unique relationship between nitial shear moduli and undrained cyclic strengths. 2) It was found that the G/G0-γ relation of an intact sample can be approximated by that of the reconstituted sample depending on the initial shear modulus of the intact sample. Based on this fact and the relationship mentioned in 1), a simplified method to evaluate undrained cyclic strength of gravelly soil by shear modulus of the ground, which was calculated using both initial shear modulus of the ground and the G/G0-γ relation of the disturbed sample, was proposed. 3) It was revealed that reduction in shear modulus with an increase in shear strain is closely related to void ratio. Based on this fact and the relationship mentioned in 1), a more simplified method to evaluate undrained cyclic strength of gravelly soil by initial shear modulus and void ratio of the ground was proposed.