Undrained cyclic loading triaxial tests were conducted on four kinds of saturated sands and it was concluded that: 1) The susceptibility to liquefaction differs according to types of sands except the influence of known factors such as relative density and mean grain size. This may be due to the microscopic factor including shapes and structures of sand grains, which may cause some difference of compressibility in sands. 2) Since the susceptibility to liquefaction corresponds to the index on compressibility obtained from drained triaxial tests, there may be a possibility to predict liquefaction from conventional triaxial tests. 3) The angle of internal friction from dynamic tests, φ'D is smaller than that from static drained tests, φd. The ratio, tan φ'D/tan φd well corresponds to the susceptibility to liquefaction zone estimated from dynamic test results reasonably agrees with the zone, in which the N-values of standard penetration tests conducted after an earthquake vary from those before the earthquake.