It has been observed many times that foundation soil consisting of saturated sands behaved like a fluid during earthquakes and the liquefaction of foundation soil in such cases has often been the main cause of catastrophic damage to structures resulting in loss of life and property. The additional safety in the superstructure by designing it for bigger forces is not of any help in the event of liquefaction of soil during an earthquake. There fore it is extremely important to examine the possibility of liquefaction of a site during an anticipated earthquake and take remedial measures if necessary before the construction activity is started. For understanding the liquefaction behaviour of saturated sand laboratory investigations (1) on vibration tables on large size samples and (2) on traxial and simple shear apparatus under cyclic loading conditions on small samples have been carried out. From the review of the available literature conclusively it can be stated that no uniform agreement todate has been achieved from different tests performed by different investigators. The test results both quantitatively as well as qualitatively are affected by the method of test and test equipment used.